Pro Asp.net Extensibility

Pro ASP.NET Extensibility

Jörg Krause

Pro ASP.NET Extensibility Copyright © 2009 by Jörg Krause All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval system, without the prior written permission of the copyright owner and the publisher. ISBN-13 (pbk): 978-1-4302-1983-5 ISBN-13 (electronic): 978-1-4302-1984-2 Printed and bound in the United States of America 9 8 7 6 5 4 3 2 1 Trademarked names may appear in this book. Rather than use a trademark symbol with every occurrence of a trademarked name, we use the names only in an editorial fashion and to the benefit of the trademark owner, with no intention of infringement of the trademark. Lead Editor: Jonathan Hassell Technical Reviewer: Stefan Turalski Editorial Board: Clay Andres, Steve Anglin, Mark Beckner, Ewan Buckingham, Tony Campbell, Gary Cornell, Jonathan Gennick, Jonathan Hassell, Michelle Lowman, Matthew Moodie, Jeffrey Pepper, Frank Pohlmann, Douglas Pundick, Ben Renow-Clarke, Dominic Shakeshaft, Matt Wade, Tom Welsh Project Manager: Kylie Johnston Copy Editor: Katie Stence Associate Production Director: Kari Brooks-Copony Production Editor: Laura Esterman Compositor: Diana Van Winkle Proofreader: Dan Shaw Indexer: BIM Indexing & Proofreading Services Artist: April Milne Cover Designer: Kurt Krames Manufacturing Director: Tom Debolski Distributed to the book trade worldwide by Springer-Verlag New York, Inc., 233 Spring Street, 6th Floor, New York, NY 10013. Phone 1-800-SPRINGER, fax 201-348-4505, e-mail kn`ano)ju
Contents at a Glance

About the Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi About the Technical Reviewer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii

CHAPTER 1

Understanding ASP.NET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

CHAPTER 2

Worker and Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53

CHAPTER 3

Modules and Handlers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107

CHAPTER 4

Providers and Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153

CHAPTER 5

Extending the Resource Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197

CHAPTER 6

Page and Session Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .245

CHAPTER 7

Security and User Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .273

CHAPTER 8

Site Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .341

CHAPTER 9

Control Extensibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .373

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .395

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Contents

About the Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi About the Technical Reviewer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii

CHAPTER 1

Understanding ASP.NET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 A Promise in Advance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 The Low-Level Architecture of Request Handling . . . . . . . . . . . . . . . . . . . . . . . . . . .1 What Is ASP.NET? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 The Lifetime of a Request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 Request Comes In . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 Getting into the .NET Runtime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 HttpContext and HttpApplication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Flowing Through the ASP.NET Pipeline . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 Modules and Handlers Using HttpModule and HttpHandler . . . . . . . . . . . . .19 The Life Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 IIS7 Integrated Pipeline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 The Application’s Pipeline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 The Request Arrives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 The Page’s Life Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 Page Request Stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 Events Fired Within the Life Cycle’s Stages . . . . . . . . . . . . . . . . . . . . . . . . . .27 Additional Page Life Cycle Considerations . . . . . . . . . . . . . . . . . . . . . . . . . .29 Dynamic Controls and Data Binding Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 Dynamic Control Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 Data Binding Events for Data-Bound Controls . . . . . . . . . . . . . . . . . . . . . . .30 Login Control Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 View State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 Why Understanding View State Is Important . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 A Word Regarding Control State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 The Page Cycle from the View State Perspective . . . . . . . . . . . . . . . . . . . . . . . . . .33 Step One—Instantiation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 Step Two—Initializing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39 Step Three—Loading the View State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39 Step Four—Loading Postback Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 Step Five—Loading Step . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 v

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Step Six—Raising Postback Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 Step Seven—Storing the View State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 Step Eight—Rendering the Page . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 The True Role of View State. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 View State Anti-Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44 Forcing a Default. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 Persisting Constant Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 Persisting Cheap Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 Initializing Child Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48 Attaching Dynamic Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50 Initializing Dynamically Created Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . .51 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52

CHAPTER 2

Worker and Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53 Managing the Worker Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53 Managing Worker Processes and AppDomains in IIS7 . . . . . . . . . . . . . . . .53 Understanding and Using Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70 ASP.NET Thread Usage on IIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70 Tune the Threading. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73 Threading and Asynchronous Operations. . . . . . . . . . . . . . . . . . . . . . . . . . . .77 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .105

CHAPTER 3

Modules and Handlers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107 Module, Handlers, and IIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107 Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108 IIS7 Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108 The IIS7 Managed Module Starter Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113 Building a Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115 Interaction Between Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119 Configuration and Deployment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .120 Handlers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .122 Built-In Handlers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .122 Extending ASP.NET Using Http Handlers . . . . . . . . . . . . . . . . . . . . . . . . . . .122 Building a Handler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124 Advanced Usage of Handlers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136 Asynchronous Pages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .138 Prepare Pages for Asynchronous Operation. . . . . . . . . . . . . . . . . . . . . . . . .138 Using a Public Web Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .140 Configuration and Deployment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143

NC O N T E N T S

Testing and Debugging Modules and Handlers . . . . . . . . . . . . . . . . . . . . . . . . . . .146 Debug Using IIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .147 Set Up Tracing for Handlers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .152

CHAPTER 4

Providers and Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153 The Provider Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153 Goals of the Provider Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .154 Default Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .154 Built-In Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .156 Extending Built-In Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .156 The Anatomy of a Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157 Making the Provider Available . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158 Configuring the Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158 General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160 Initialization Procedure of a Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160 Lifetime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161 Thread Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161 Creating a Custom Provider-Based Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .163 Limitations of the Code Samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .163 Creating a Service. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .164 Creating the Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .165 Configuring Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .170 Using the Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .172 Extending the Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .174 How to Scaffold a Configuration Section . . . . . . . . . . . . . . . . . . . . . . . . . . .174 Anatomy of a Configuration Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .174 The Class Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175 Attributes to Control Elements’ Behaviors . . . . . . . . . . . . . . . . . . . . . . . . . .176 Definition of a Simple Configuration Section . . . . . . . . . . . . . . . . . . . . . . . .176 Usage of a Custom Configuration Section . . . . . . . . . . . . . . . . . . . . . . . . . .180 Accessing the Configuration Declaratively . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .181 Extending the Expression Binding Syntax . . . . . . . . . . . . . . . . . . . . . . . . . .181 Introduction to Expression Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .181 Creating an Expression Builder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183 Accessing Settings for Non-Compiled Pages . . . . . . . . . . . . . . . . . . . . . . . .187 Beyond Simple Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188 Design-Time Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189 Implementing an Expression Builder with Design-Time Support . . . . . . .190 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195

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CHAPTER 5

Extending the Resource Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197 Principles of Resource Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197 The Fallback Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197 Using Global Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 Limitations of the Existing Provider. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 Programming a Custom Resource Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 Extending the Provider Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200 Implementing the Custom Provider. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .201 Configure the Resource Provider. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208 Using the Custom Resource Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208 Implementing Design-Time Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209 Register the Design-Time Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209 Edit Resources at Runtime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .219 How It Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .219 Creating an Online Editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .223 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .243

CHAPTER 6

Page and Session Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .245 The Page State Persister . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .245 A Look Back. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .245 The Default Page State Persister . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .246 State Storage in ASP.NET. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .246 Persisting Page State Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .247 View State Explained . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .247 Control State Explained . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .247 The Default Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .249 Changing the Default Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .251 Developing a Custom Page State Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .251 Choosing the Data Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .252 Analyzing a Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .252 Implementing the Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .252 Extending the Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .254 Maintaining the Storage by Using the Health Monitor. . . . . . . . . . . . . . . . .254 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .256 Session State Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .256 The Session State Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .256 Identifying the Session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .258 The Internal State Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .260 Improving the Session State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .263 Implementing the Session State Store Provider . . . . . . . . . . . . . . . . . . . . . . . . . .264 The Session State Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .264

NC O N T E N T S

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .266 Implementation of a File-Based Session State Persister . . . . . . . . . . . . . .267 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .272

CHAPTER 7

Security and User Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .273 Built-In Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .273 Authentication Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .276 Authorization Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .276 The User Management Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .277 Extending Membership and Role Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .281 Why Create a Membership Provider? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .281 Solution Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .282 Developing Membership and Role Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . .282 Create Web Service–Driven Membership Provider . . . . . . . . . . . . . . . . . . .282 Create Web Service–Driven Role Provider . . . . . . . . . . . . . . . . . . . . . . . . . .282 Configuring the Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .298 Implementing the Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .300 Configuring the Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .308 Testing the Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .308 Extending Profile Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .310 The Profile Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .310 Understanding the Profile Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .310 Configuring Custom Profile Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314 Implementing a Custom Profile Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314 Preparation Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314 Implementing the Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .319 A Client Side–Driven Profile Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .325 Extending Web Parts Personalization Providers. . . . . . . . . . . . . . . . . . . . . . . . . . .329 Understanding the Web Parts Personalization Provider . . . . . . . . . . . . . . .329 Implementing a Custom Personalization Provider . . . . . . . . . . . . . . . . . . . .331 Testing the Custom Web Part Personalization Provider . . . . . . . . . . . . . . .339 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .340

CHAPTER 8

Site Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .341 Site Map Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .341 Internal Site Map Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .341 Localization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .343 Security Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .343 Reasons to Write a Custom Sitemap Provider . . . . . . . . . . . . . . . . . . . . . . .343 Writing a Custom Sitemap Provider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .344 Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .344 Learning About the Base Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .344

ix

x

NCO NTENT S

Implementing a SQL Server–Based Navigation . . . . . . . . . . . . . . . . . . . . . .348 Suggestions for Extending the Example . . . . . . . . . . . . . . . . . . . . . . . . . . . .354 Extending the VirtualPathProvider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .354 Using the VirtualPathProvider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .354 Register the VirtualPathProvider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355 Prerequisites for a VirtualPathProvider . . . . . . . . . . . . . . . . . . . . . . . . . . . . .356 Helpful Classes for Path and File Operations . . . . . . . . . . . . . . . . . . . . . . . .357 Creating a Virtual Path Provider to Get Themes from Database . . . . . . . .358 Limitations of the VirtualPathProvider Approach . . . . . . . . . . . . . . . . . . . . .371 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .372

CHAPTER 9

Control Extensibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .373 Adaptive Control Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .373 The Default Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .374 Using Control Adapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .376 Using Page Adapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .379 Device-Specific Filter for Adaptive Behavior . . . . . . . . . . . . . . . . . . . . . . . .381 Using Control Adapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385 Device Friendly Adapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385 CSS Friendly Adapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385 Other Adapter Ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385 Writing a Custom Control Adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385 Steps for Creating the Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385 The Example Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .386 Why Use HtmlTextWriter? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .390 Configure the Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .390 Writing a Custom Page Adapter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .391 Steps for Creating the Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .391 Configure the Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .393 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .394

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .395

About the Author

NJÖRG KRAUSE has been working with software and software technology since the early 1980s, beginning with a ZX 81 and taking his first steps as a programmer in BASIC and assembly language. He studied information technology at Humboldt University, Berlin, but in the 1990s he left early to start his own company. He has worked with Internet technology and software development since the early days when CompuServe and FidoNet dominated. He’s been with Microsoft Technologies and Software since Windows 95. In 1998, he worked on one of the first commercial e-commerce solutions, and wrote his first book in Germany, E-Commerce and Online Marketing, published by Carl Hanser Verlag, Munich. Due to its wide success, he started working as a freelance consultant and author in order to share his experience and knowledge with others. He has written several books for Hanser, Addison-Wesley, and other major publishers in Germany—a total of more than 40 titles. He also publishes articles in magazines and speaks at conferences in Germany, including BASTA. Currently, Jörg works as a senior consultant for Microsoft Technologies at Computacenter AG & Co. oHG in Berlin. In his occasional spare time, Jörg enjoys reading thrillers and science fiction, as well as playing badminton in the winter and golf in the summer.

xi

About the Technical Reviewer

NSTEFAN TURALSKI is a nice chap who is capable of performing both magical and trivial things with a little help from code, libraries, tools, APIs, and servers. Wearing many hats, he has experience in almost all aspects of the software life cycle, and is especially skilled in business analysis, design, implementation, testing, and QA, as well as team management. His main areas of interest are quite wide but include emerging technologies with recent focus on RIA (Silverlight and AIR), cloud computing, functional programming, and software engineering at large. Before he realized that he enjoys criticizing other people’s work more, Stefan published several technical articles mainly about .NET technology, SOA, software engineering, and mobile development. For the last 10-plus years, he has been building solutions ranging from Perl scripts, integrations of SQLite, and Web sites, to highly scalable .NET and COM+ enterprise-class systems. Feel free to contact him at opab]j*pqn]hoge
xiii

Acknowledgments

I

’d like to mention the people who helped me create this book and make it what it is. First, I’d like to thank David White and his daughter, Rebekah, for their amazing work smoothing my style and cajoling it into readable English. I know you had a challenging task. I can’t forget the support from Jonathan Hassell for my first steps into the Apress world, as well as the continuing help from Kylie Johnston. Thanks for your frequent reminders about the deadline, Kylie. They really motivate lazy writers back to the keyboard. Thanks to our technical reviewer, Stefan, who opened my mind with his remarks and code style ideas, and pointed out the mistakes that I made in haste. His work greatly improved the quality of this book. Last, but not least, I’d like to thank my family and friends for understanding when I went back to the computer to continue writing or fighting with Visual Studio, while they sat on the terrace for a barbeque. Believe me, it was much harder for me than for you.

xv

Introduction

What Does This Book Cover? ASP.NET is an established and well-known web application framework, and there are several books on the market with different emphases and at different levels. However, ASP.NET is becoming more and more a foundation technology upon which larger and larger projects are being built. Developers are facing increasing complexity and greater demands to fulfill in their daily tasks. This book examines in-depth the technology beyond the basic ASP.NET topics available elsewhere. It’s full of practical tips and tricks from an experienced developer. You’ll learn not only how things work, but also why. By adopting this knowledge, you will succeed in extending and adapting highly useful functionality in your own projects. Extensibility is covered in great depth. Developers have a tendency to use a framework, language, or piece of software “as is.” Even in the age of open source software, most developers don’t look inside existing code or attempt to adapt it to fit their needs. Instead, they write their own code. For years, I’ve been asking developers why they avoid third-party code and go to such lengths in order to write essentially the same software. It’s usually because if they’ve created it, they know that they can control, understand, and master it. With .NET 2.0, Microsoft shifted the ASP.NET framework towards a new paradigm—the paradigm of extensibility. This allows developers to extend Microsoft’s software and adapt the parts to behave exactly as you would have designed. Microsoft encourages you to change existing behaviors, add features, modify settings, and basically do whatever you want in order to get the most out of their framework. However, never ignore infrastructure parts of the framework or replace them completely with your own code. Almost every ASP.NET book explains ASP.NET from the ground up—some are in-depth and some provide clear details, but ASP.NET is always treated “as is.” Their failing is in treating ASP.NET like concrete—when, in fact, it’s like Lego™. My underlying motivation for writing this book was to educate developers about this overlooked aspect of ASP.NET: the many ways it can be extended.

Conventions Used in This Book We understand that you’re eager to start reading and learning, but it is worth taking a few seconds to look over this section—it will help you to get the most out of this book. Several icons and font conventions are used throughout:

s 3CREENMESSAGES CODELISTINGS ANDCOMMANDSAMPLESAPPEARINikjkol]_apula.



s 4HESAMEikjkol]_abkjp is used for HTML, ASP.NET controls (declarative listings), and XML snippets.



s )MPORTANTPARTSOFALISTINGAREHIGHLIGHTEDIN^kh`ikjkol]_a.



s #ODE RELATEDTEXTINCLUDESMANYREFERENCESTOCODE SUCHASMETHODNAMES CLASSNAMES namespaces, members, and so on. This is a mixture of common framework names and the ones I’ve used in examples. To distinguish between them, all framework names (from the Microsoft world) are set in ikjkol]_a, while all private names are set in italics.



s 4OEMPHASIZEORQUOTETHINGS hQUOTESvAREOCCASIONALLYUSED xvii

xviii

NINT ROD UCTIO N

Several icons highlight important definitions, cautions, and conclusions.

NTip

This is a tip.

NNote

A note that explains a topic further but is not required for understanding the main topic.

NCaution

A warning to keep you from common pitfalls.

Who This Book Is For This book is intended for advanced web developers interested in learning about the internal workings of ASP.NET. I assume that you already have some experience writing small web applications, that you’ve actively created some web projects, and you want to take your skills a step further. What if your next customer wishes to run a large server cluster, a site with thousands of pages, complex navigation, and heavy database access? ASP.NET can handle this, but its out-of-the-box features won’t be adequate. This book covers situations such as these in detail and shows you what to do when ASP.NET reaches its limits. You’ll learn how to extend, customize, and enhance this platform to get what you want. “No more compromise” is my motto. Throughout my years of experience programming ASP.NET, I’ve noticed that developers often complain about incorrect behavior, supposed bugs, incomplete implementations, or missing features. In most of these situations, I don’t agree that ASP.NET is deficient or faulty. I’ll demonstrate that the key to success with ASP.NET is a deep understanding of the platform that goes beyond the basics. ASP.NET is not perfect—it has its rough edges, like any other piece of software. However, Version 3.5 is top-of-the-line, providing almost everything you need in order to get your professional projects functioning well. Really, really well. This is what I’d like to tell you: learn, explore, understand, and you will be the professional developer you want to be. I also assume that you already have some basic knowledge of skills and technologies often required as a web developer:

s (4-, #33 AND*AVA3CRIPT



s 6ISUAL3TUDIOBASICS SUCHASCREATINGAPROJECT RUNNING ANDDEBUGGINGIT



s !30.%4BASICS SUCHASPUTTINGACONTROLONTOTHEPAGE CUSTOMIZINGIT CREATINGAUSEROR custom control, and so on



s "ASICKNOWLEDGEOFHOWTOOBTAINDATABASEACCESS ASWELLASUSING,).1TOQUERYITAND write data back



s 5SING8-,ASEITHERADATASOURCEORSTORAGE

There is no information specific to the topics in this book, but I use all of these techniques with the example code.

NI N T R O D U C T I O N

Prerequisites This book is based on ASP.NET 3.5. As a basic platform, I use Visual Studio 2008, running on Windows Server 2008 with IIS7. When a client is involved, I use Windows Vista SP1. A similar platform is helpful for getting samples running. Because the last radical change in IIS took place between IIS5 and IIS6, it’s not possible to transform anything to IIS5 level. However, much of the information pertaining to IIS7 may also be true for IIS6—a bit of backward compatibility! Nevertheless, I’d encourage you to look to the future and work with the most current tools and platforms you can obtain.

How This Book Is Organized There are many ways of structuring a book. From my long-term experience in writing and publishing books, I know that people read books very differently. Some read from beginning to end, just like a novel, while others start where they find an interesting topic. There is no book that can cover all reading styles! However, this book follows the same successful strategy I’ve used many times before. I start with the basics: low-level concepts and background information necessary to really understand a theme. Then I proceed systematically through all sections in an independent order. This allows you to read from beginning to end—or to dip into an interesting chapter and skip the others. The many references in the book, pointing to sections where related parts are described in more detail, will help you get the information you need. This book is full of code and examples, which are all available for download at sss*]lnaoo* _ki in the Downloads section of this book’s home page. Included with the package are subfolders named after each chapter: “chapter01,” “chapter02,” etc. These folders contain several sample solutions or Web sites in separate folders. Almost all examples are fully functional. Smaller code snippets that can’t run on their own aren’t included to avoid confusion.

xix

C HAPTER

1

Understanding ASP.NET

T

his chapter looks under the covers of ASP.NET. Many fundamentals of ASP.NET just scratch the surface, but to get the most out of the framework it is a good idea to look much deeper. This chapter includes:

s (OW!30.%4WORKSINTERNALLYANDTHERELEVANTFEATURESNEEDEDFORYOUREVERYDAYTASKS



s 4HEBEHIND THE SCENESCONCEPTSTHEAPPLICATIONLIFECYCLE THEPAGELIFECYCLE ANDTHECON trol creation process



s 4HESTEPSTAKENTOTRANSLATEYOUR&*]olt and &*_o files into compiled code



s 4HECOMMON!30.%4FEATURES SUCHASFORMSTICKINESSANDVIEWSTATE ANDBEYOND

A Promise in Advance !30.%4ISAPOWERFULANDFLEXIBLEARCHITECTUREFORBUILDINGWEBAPPLICATIONS4HEHIGH LEVELPARTSˆ 7EB&ORMSAND7EB3ERVICESˆAREWELLKNOWN(OWEVER ASYOURAPPLICATIONSSCALEUPINREALLIFE sooner or later you encounter performance issues, or find that things which seemed easy become CHALLENGING4HATISWHATTHISBOOKPROVIDESˆALOOKBEYONDTHEBIGPICTURE4HELITTLEDETAILSARE harder to understand and sometimes more abstract, less fun for more work. But let me begin with a promise: it’s worth the effort.

The Low-Level Architecture of Request Handling Understanding the innermost parts of a platform is highly satisfying. You will feel confident know ing that you can write better applications and recognize why they work. In this section, you will examine the internals of ASP.NET in order to understand how requests flow through the processing pipeline. A processing pipeline is a chain of processing elements arranged so that the output of one is the input of the next. According to ASP.NET, these elements are the internal steps required to pro cess a request. This is not aimed at those learning the basics or creating a simple interactive page. This is what you need to know when you write or build large sites that involve hundreds of pages handling requests from thousands of users. 7EB&ORMSAND7EB3ERVICESAREBOTHSOPHISTICATED HIGH LEVELIMPLEMENTATIONSOF(440HAN DLERS(440HANDLERS are parts of the processing pipeline that manage incoming requests that use the (YPERTEXT4RANSFER0ROTOCOLBYCREATINGTHEREQUIREDCONTENT4HEYAREBUILTONTOPOFTHE!30.%4 framework and exposed as one of the default project templates in Visual Studio. Most developers are happy with these project types, and are ignorant of, or misunderstand, the additional potential that EXISTS4HEBASIC(440HANDLERSAREBUILTWITHMANAGEDCODE4HISMEANSTHATYOUCANGETHIGHLYCUS tomized behavior processing requests through the pipeline by using your very own code. 1

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C H APT ER 1 N UNDER S TA NDING A S P . NET

What Is ASP.NET? In general terms, ASP.NET is a request processing engine. It takes an incoming request and passes it through its internal pipeline to an end point, where you as a developer can attach code to process that REQUEST4HISENGINEISCOMPLETELYSEPARATEFROM(440RUNTIMEANDTHE7EB3ERVER)NFACT THE(440 runtime is a component that you can host in your own applications outside of Internet Information Services (IIS) or any server side application altogether. Visual Studio and the integrated development server is a good example of an implementation that is neither based on nor related to IIS. 4HE(440RUNTIME is responsible for routing requests through this pipeline, a complex yet very elegant mechanism. Several interrelated objects, extensible via subclassing or through interfaces, are available for customization work. This makes the framework highly adaptable. In this book, I’ll cover most of these extensibility points and show that there are virtually no limits when using ASP.NET. 4HROUGHTHISMECHANISMITSPOSSIBLETOHOOKINTOLOW LEVELINTERFACES SUCHASAUTHENTICATION authorization, and caching. You can even filter content by routing incoming requests that match a specific signature directly to your code. Of course, there are a lot of different ways to accomplish THESAMETHINGˆBUTALLOFTHEAPPROACHESARESTRAIGHTFORWARDTOIMPLEMENT The Internet Service API1 (ISAPI) is a common Win32 API. The ASP.NET engine interfaces with IIS through an ISAPI extension. This extension hosts .NET through the ASP.NET runtime. The ASP. NET engine was written entirely in managed code, and all of the extensibility functionality is pro vided via “managed code extensions.” The impressive part of ASP.NET is that it is very powerful but simple to work with. Despite its breadth and complexity, accomplishing your desired outcomes is easy. ASP.NET enables you to perform tasks that were previously the domain of ISAPI extensions ANDFILTERSON))3)3!0)ISALOW LEVEL7IN!0)THATHASAVERYSPARTANINTERFACE&OR.%4DEVELOP ers it could be very difficult to develop anything on top of this interface. Writing ISAPI filters in C++ ISNOTINCLUDEDINMOSTCURRENTAPPLICATION LEVELDEVELOPMENT(OWEVER SINCE)3!0)ISLOW LEVEL it is likely very fast. Thus, for some time ISAPI development has been largely relegated to providing BRIDGEINTERFACESTOOTHERAPPLICATIONORPLATFORMS SUCHAS0(0"UT)3!0)DIDNOTBECOMEOBSOLETE with the appearance of ASP.NET. ISAPI provides the core interface from the Web Server, and ASP.NET uses the unmanaged ISAPI code portion to retrieve input and send output back to the client. The content that ISAPI provides is passed using common objects like DpplNamqaop and DpplNaolkjoa that expose the unmanaged data as managed objects. Back in the .NET world it becomes very easy to use these objects in your own code. I’ll discuss later in the section “Getting into the .NET Runtime” how the unmanaged and man aged world interoperate.

The Lifetime of a Request The lifetimeSTARTSWITHAN(440REQUEST7HENEVERTHEUSERTYPES in a URL, clicks on a hyperlink, or SUBMITSAN(4-,FORMONTHEBROWSER AREQUESTISSENTTOTHESERVER

NNote

It’s essentially the same for Web Services. A client application calls an ASP.NET–based Web Service by sending a request. Therefore, I refer to the term Request and don’t differentiate between Web Service and browser requests. You can assume that the examples given are intended to run in a browser environment.

For the sake of clarity, I left out the steps made behind the scenes in the browser and through the protocol stacks. This includes port assignment within the TCP/IP stack and name resolution using the DNS protocol. As long as we’re talking about ASP.NET, there is no direct influence on DNS, so let’s keep this in mind but not complicate the description with side effects. 1. API means Application Programming Interface.

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DOMAIN NAME SYSTEM The Domain Name System (DNS) is hierarchical naming system for internet resources. Mainly these are computers that get human readable names—the hostnames—the DNS translates into IP addresses. Beginning with some root servers, the DNS is a hierarchy of name resolution servers for particular levels of the hostname. The protocol running between the servers and clients is called DNS protocol. .NET Framework supports DNS with several classes. However, for ASP.NET applications usually there is no need to program directly against this low-level protocol. The request focused on begins when the name resolution process is done.

On the server side the Web Server picks up the request. In this description, I’ll focus mainly on IIS7 with some words for IIS6, which is still widely used. Additionally, I focus on preferred mode RUNNING!30.%4ON))3ˆTHEINTEGRATEDMODE(OWEVER MOSTPARTSWILLNOTREFERTOASPECIFIC version, so the term IIS covers all from IIS5 to IIS7 (and beyond, probably). Within IIS the request ISUSUALLYROUTEDTOTHEASPXPAGE(OWTHISPROCESSWORKSINTERNALLYDEPENDSENTIRELYONTHE(440 handler that handles the request. The mapping between the .aspx extension and the ISAPI DLL, aspnet_isapi.dll, is responsible for this. Every request you want served by ASP.NET must be routed BYITSASSIGNEDAPPLICATIONEXTENSION4HISMEANSTHATTHEEXTENSIONISAPRE DEFINED YETVOLUNTARY DEFINITION)MAGINEIFYOUMAPPEDHTMLPAGESTOBEPROCESSEDBY!30.%4ASWELLˆITWOULDNTBE OBVIOUSTHAT!30.%4WASDOINGTHETRICK(ENCE THEEXTENSIONISTHEBASICMAPPINGWHERETHEPRO cessing starts. This means, too, that different extensions might route to different handlers. For instance, the *]oit extension is routed to the Web Service handler. Instead of opening a page and starting a page parser, this request does not open a file but a specially attributed class that identifies the implemen tation. Many other handlers are installed with ASP.NET, and you are also able to define your own. All of these handlers are mapped to the ASP.NET ISAPI extension and configured in web.config to GETROUTEDTOASPECIFICIMPLEMENTATION3EETHEFOLLOWINGEXAMPLEIN,ISTING FROMGLOBALDEFINI tion web.config file that holds the majority of default mappings. Listing 1-1. Extract of Global web.config Showing Some of the Default Mappings 8dpplD]j`hano: 8]``l]pd9pn]_a*]t`ran^9&pula9Ouopai*Sa^*D]j`hano*Pn]_aD]j`han± r]he`]pa9pnqa+: 8]``l]pd9Sa^Naokqn_a*]t`ran^9CAP± pula9Ouopai*Sa^*D]j`hano*=ooai^huNaokqn_aHk]`anr]he`]pa9pnqa+: 8]``l]pd9&*]t`ran^9&pula9Ouopai*Sa^*DpplJkpBkqj`D]j`hanr]he`]pa9pnqa+: 8]``l]pd9&*]oltran^9&± pula9Ouopai*Sa^*QE*L]caD]j`hanB]_pknur]he`]pa9pnqa+: 8]``l]pd9&*]odtran^9&± pula9Ouopai*Sa^*QE*OeilhaD]j`hanB]_pknur]he`]pa9pnqa+: 8]``l]pd9&*]oitran^9&± pula9Ouopai*Sa^*Oanre_ao*Lnkpk_kho*Sa^Oanre_aD]j`hanB]_pknu(± Ouopai*Sa^*Oanre_ao(Ranoekj9.*,*,*,(?qhpqna9jaqpn]h(± Lq^he_GauPkgaj9^,/b1b3b--`1,]/]r]he`]pa9b]hoa+: 8]``l]pd9&*]o]tran^9&± pula9Ouopai*Sa^*DpplBkn^e``ajD]j`hanr]he`]pa9pnqa+: 8]``l]pd9&*]o_tran^9&± pula9Ouopai*Sa^*DpplBkn^e``ajD]j`hanr]he`]pa9pnqa+: 8]``l]pd9&*i]opanran^9&± pula9Ouopai*Sa^*DpplBkn^e``ajD]j`hanr]he`]pa9pnqa+:

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8]``l]pd9&*ogejran^9&± pula9Ouopai*Sa^*DpplBkn^e``ajD]j`hanr]he`]pa9pnqa+: 8]``l]pd9&*^nksoanran^9&± pula9Ouopai*Sa^*DpplBkn^e``ajD]j`hanr]he`]pa9pnqa+: 8]``l]pd9&*oepai]lran^9&± pula9Ouopai*Sa^*DpplBkn^e``ajD]j`hanr]he`]pa9pnqa+: 8]``l]pd9&*_kjbecran^9&± pula9Ouopai*Sa^*DpplBkn^e``ajD]j`hanr]he`]pa9pnqa+: 8]``l]pd9&ran^9CAP(DA=@(LKOP± pula9Ouopai*Sa^*@ab]qhpDpplD]j`hanr]he`]pa9pnqa+: 8]``l]pd9&ran^9&± pula9Ouopai*Sa^*DpplIapdk`Jkp=hhksa`D]j`hanr]he`]pa9pnqa+: 8+dpplD]j`hano: In the extract, you find a handler that services a request, like L]caD]j`hanB]_pknu for &*]olt pages, as well as some that suppress access to the extension, like DpplBkn^e``ajD]j`han for &*_kjbec files.In coding terms the handler is a type, implemented by a .NET class that handles a specific extension. You can also attach your own handlers to existing extensions and route the request through both your own and the default implementation. A summary of all basic mappings ALREADYAVAILABLEARESHOWNIN4ABLE  Table 1-1. Application Mappings Assigned to aspnet_isapi.dll

Extension

Resource Type

Comments

*]o]t

ASP.NET application files

Usually the global.asax file only.

*]o_t

ASP.NET user control files

Usually these files are not called directly.

*]odt

(440HANDLERS

4HEMANAGEDCOUNTERPARTOF)3!0)EXTENSIONSSEE Chapter 3 for details.

*]oit

ASP.NET Web Services

Obsolete since the appearance of Windows Communication Foundation (WCF).

*]olt

ASP.NET web pages

The regular page handler.

*]t`

!30.%4INTERNAL(440HANDLER

5SEDFOREMBEDDEDRESOURCESLIKE*AVA3CRIPTOR images pulled from compiled code.

*or_

7EB3ERVICEHANDLER

7#& BASEDSERVICESNOWHASITSOWNEXTENSION

Let’s talk about the &*]oit extension shown in the table. With the introduction of .NET 3.0, Microsoft moved all the communication stuff like .NET remoting and Web Services to Windows Communication Foundation (WCF) base library.24HISMEANSTHATTHE!30.%4 BASED7EB3ERVICES are superseded. Even though they are still fully supported, it makes sense to consider moving Web Service projects from ASP.NET platform to WCF. It’s not a significant change, as most classes are SIMILARAND7#&HASSOMEMOREPOWERFULAPPROACHES(OWEVER )DONTCOVER7#&INTHISBOOK and therefore the following description is limited to the ASP.NET portion.

From ISAPI to ASP.NET The purpose of ISAPI is to access a Web Server like IIS on a very low level. The interface is optimized for performance, but it’s also very simple and straightforward. For most developers with .NET expe rience it’s pretty hard to use, because the coding style you use in .NET to, say, create sophisticated infrastructure solutions, is the opposite of the style you see when coding ISAPI extensions in C++. 2. The old assemblies and namespaces are still supported, of course.

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-ANYHIGH LEVELWEBDEVELOPMENTLANGUAGESSUCHAS0(0 0ERL ANDEVEN!30.%4 AREBUILTON top of ISAPI. ISAPI is good for writing such environments. For application developers it’s not the best way to WRITEOURSITESONTIMEANDWITHINBUDGET(OWEVER )3!0)ISTHELAYERTHE!30.%4ENGINEISBUILT on, and a good understanding of the relation between ISAPI and ASP.NET is helpful for getting the most out of ASP.NET. For ASP.NET the ISAPI level is just acting as a routing layer. The heavy stuff, such as processing and request management, occurs inside the ASP.NET engine and is mostly done in managed code. You can think of ISAPI as a sort of protocol. This protocol supports two flavors, ISAPI extensions AND)3!0)FILTERS%XTENSIONSACTASATRANSACTIONINTERFACETHEYHANDLETHEFLOWOFDATAINTOANDOUT of the Web Server. Each request coming down the pipeline is going through the extensions and the code decides how they are treated. As you might imagine, ASP.NET is such an extension. ASP.NET has several ways to give you as much control as possible to hook into this extension and modify THEDEFAULTBEHAVIOR4HELOW LEVEL)3!0)INTERFACESARENOWAVAILABLEASHIGH LEVEL.%4INTERFACES named EDpplD]j`han and EDpplIk`qha. This is very powerful and still provides good performance, BECAUSEITSAWELL WRITTENBALANCEBETWEENLEANACCESSTOTHELOWERLEVELANDANEASY TO USEHIGH level API. Like any other ISAPI extension, the code is provided as a DLL and is hooked into the IIS man agement. You can find this DLL here: 8*JAPBn]iaskng@en:X]oljap[eo]le*`hh. If you have several versions of .NET framework installed, you may wonder why there is just one such DLL in the tree. I predict that you will find this in the v2.0.50727 folder or at least in one with v2.0 at the beginning. If you have .NET 1 installed, another version might reside in a folder named v1.1.*. The reason is that Microsoft has added a lot of features in .NET 3.0 and .NET 3.5 regarding ASP.NET, BUTITSINTERFACESTOTHELOW LEVELPORTIONARESTILLTHESAME!LLNEWFUNCTIONALITYISCOMPLETELYWRITTEN in managed code. This is indeed a transition, as it shows that it’s possible to write infrastructure com ponents in managed code. With powerful hardware the performance loss is not that critical, whereas the benefits regarding security, reliability, and shorter development cycles matter.

NNote

With the upcoming .NET 4.0, a new engine appears on the horizon that is closer to IIS7 and has several internal improvements. For now, it seems as though most of the techniques and internal behaviors described here have barely changed.

Extension Mapping As you have already seen, the Web Server recognizes resource requests by analyzing the file exten sion. The first step to get the ASP.NET ISAPI extension running is a mapping between the several file types and the DLL I mentioned earlier. In IIS7 you can see this by following these steps: 1. Open Internet Information Services (IIS) Manager. 2. Choose the server node. 3. In the right pane scroll to the IIS table. 4. $OUBLE CLICK(ANDLER-APPINGS In the table you will see a column Path with the extensions already assigned. In the column (ANDLERYOUWILLSEETHEASSIGNEDMODULE&ORTHE&*]olt extension you will see the following mappings:

s 0AGE(ANDLER&ACTORY )NTEGRATED



s 0AGE(ANDLER&ACTORY )3!0) 



s 0AGE(ANDLER&ACTORY )3!0)  ONA BITSYSTEMONLY

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!DDITIONALLY WITH.%4 3TWOADDITIONALMAPPINGSAREINSTALLEDONA BITMACHINE 

s 0AGE(ANDLER&ACTORY )NTEGRATED 



s 0AGE(ANDLER&ACTORY )3!0) ?BIT

For the unmanaged side you will see the Eo]leIk`qha handler and for the managed one .NET TYPESUSEDTOHANDLETHEPAGES&IGURE SHOWSPARTOFTHEMAPPINGTO)3!0)EXTENSION

Figure 1-1. IIS7 maps extensions like *.aspx to ISAPI extensions. If the mapping isn’t there, ASP.NET is probably not correctly installed. Don’t try to map this by hand. There is a lot of configuration that happens behind the scenes. Because you probably have several ASP.NET versions running parallel on the same machine, your application might fail to work JUSTBYCOMPLAININGABOUTWRONGVERSION4HISDOESNOTREQUIREYOUTORE REGISTERTHEVERSIONNEEDED Applying the appropriate version is made in the application pool settings. In IIS6 the properties of a specific site of a Web Server let you choose the right framework. In IIS7 it has been moved to the application pool settings dialog. Each application pool can run only one version of the runtime. To set another framework for a specific site, you have to create another application pool, set the appropriate FRAMEWORKVERSION ANDASSIGNTHEAPPLICATIONPOOLTOTHESITE ASSHOWNIN&IGURE  (OWEVER IFTHEINSTALLATIONISDESTROYEDORINCOMPLETE ATOOLMIGHTHELP4OREGISTEROR RE REGISTERTHEMAPPINGS JUSTINVOKETHEFOLLOWINGCOMMAND _`8*JapBn]iaskng@ena_pknu: ]oljap[naceeo)e Again, this command is not available for all .NET framework versions. The tools delivered with 6ERSIONWILLDOTHETRICK EVENIFYOURUNOR7ITH!30.%4 ANEW)3!0)$,,WILLBE INTRODUCEDˆBUTBACKWARDCOMPATIBILITYISSTILLGUARANTEED)FYOUSTILLHAVE6ERSIONXSITESRUN ning, another version is available. It’s a bit tricky, but in order to run two different ASP.NET versions, just register with the highest available.

3. Naming not yet finalized at date of printing

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Figure 1-2. Add a new application pool and get the right framework there.

Request Comes In When a request comes in, IIS checks for the script map and routes the request to the associated extension. In the case of ASP.NET let’s assume that the request is something like Default.aspx, so it’s BEINGROUTEDTOASPNET?ISAPIDLLSEE&IGURE   I assume that you have already worked with and probably configured the application pool. The application pool was introduced with IIS6 and allows the complete isolation of applications from each other. This means that IIS is able to completely separate things happening in one application from those in another. Putting applications together in one pool could still make sense, because another pool would create its own worker process and could use up many resources. Each applica tion pool is represented by separate worker process and seen on the list of processes as a separate entry. Separate applications make the Web Server more reliable. If an application hangs, consumes too much CPU time, or behaves unpredictably, it influences its entire pool. Other application pools (and the applications within them) will continue to run. Additionally, the application pools are highly configurable. You’ve already learned that the framework version can be different for each pool, which is very useful for migration scenarios. You can configure the security environment by choosing the impersonation level and customizing the rights given to a web application. Applica tion pools are executables that run as any other program. This makes them easy to monitor and configure. Although this does not sound very “low level,” application pools are highly optimized to talk directly to the kernel mode driver http.sys. Incoming requests are directly routed to the pool attached to the application. At this point, you might be wondering where InetInfo has gone. You may have heard of it in the context of previous versions of ASP.NET. If not, it’s just a helper process mainly used for debugging purposes of Internet Information Services. It is still there, but it is basi cally just an administration and configuration service. The flow of data through the IIS system goes as directly and quickly as possible, straight down from http.sys to the application pools. This is one reason why IIS7 is much faster and more reliable than any other IIS before it. An IIS7 application pool also has intrinsic knowledge of ASP.NET and in turn ASP.NET can COMMUNICATEWITHTHENEWLOW LEVEL!0)STHATALLOWDIRECTACCESSTOTHE(440#ACHE!0)S4HIS can offload caching from the ASP.NET level directly into the Web Server’s cache, which again will improve performance drastically. In IIS7, ISAPI extensions run in the Application Pool’s worker process. The .NET runtime also runs in this same process, and consequently communication between the ISAPI extension and the .%4RUNTIMERUNShIN PROCESS vWHICHISINHERENTLY more efficient.

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Figure 1-3. Request flow through IIS and down to ASP.NET runtime (simplified)

Getting into the .NET Runtime Now let’s look at what happens to the request when accessing the managed level. The worker process w3wp.exe hosts the .NET runtime, and the ISAPI DLL calls into a small set of unmanaged INTERFACESVIALOW LEVEL#/- Unfortunately, not much information is available from Microsoft. Apart from a few blogs that one can’t always trust, it’s hard to say how the interaction between ASP. NET and ISAPI is made. Reading the manual doesn’t help either. Microsoft states that the API “sup ports the .NET Framework infrastructure and is not intended to be used directly from your code,” which confirms the existence of the interface but nothing more. Using a disassembly tool like .NET Reflector (from na`)c]pa*_om) is one way to look into the details. Let’s examine the System.Web DLL, which contains everything we’d like to know. First,  #OMPONENT/BJECT-ODEL ANINTERFACESTANDARDFORSOFTWARECOMPONENTRY

C H A P T E R 1 N U N D E R S T A N D I N G A S P . N E T

the entry point is the namespace Ouopai*Sa^*Dkopejc, where you’ll see how the runtime interacts WITHTHE)3!0)PART ASSHOWNIN&IGURE 

Figure 1-4. If there is no information available, you can use Reflector to reveal the internal code. If the runtime handles a request, it calls the Lnk_aooNamqaop method of the EEO=LENqjpeia inter face. The interface is part of ISAPI and exposed as COM. The first parameter will return a pointer WHICHGIVESACCESSTOTHE)3!0)MODULEASSHOWNIN,ISTING  Listing 1-2. Definition of the ProcessRequest Method Wnapqnj6I]nod]h=o$Qji]j]ca`Pula*E0%Y ejpLnk_aooNamqaop$WEjYEjpLpna_^(± WEj(I]nod]h=o$Qji]j]ca`Pula*E0%YejpqoaLnk_aooIk`ah%7 The parameter called “ecb” returns the ISAPI Extension Control Block (ECB, (Microsoft)) that is passed as an unmanaged resource. The method takes the ECB and uses it as the base input and OUTPUTINTERFACEUSEDWITHTHE2EQUESTAND2ESPONSEOBJECTS!N)3!0)%#"CONTAINSALLLOW LEVEL request information. This includes server variables, an input stream for form variables, as well as an output stream that is used to write data back to the client. The output is later accessible via the Response objects, but you can see the tight relation between incoming request and outgoing response. The ecb pointer basically provides access to the functionality of an ISAPI request. The Lnk_aooNamqaop method is the entry and exit point where this resource initially enters the street up to our managed code world and where the managed processing ends.

Threads and Processes So far thingsARENOTQUITEEASY BUTTHEFLOWOFTHEREQUESTTHROUGHTHECODEISSTRAIGHT(OWEVER in real life things tend to become more complex. The ISAPI extension runs requests asynchro nously. This means that the ISAPI extension immediately returns on the calling worker process or IIS thread, but keeps the ECB for the current request alive. The ECB then includes a mechanism for letting ISAPI know when the request is complete. This asynchronous processing releases the

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ISAPI worker thread immediately, and forwards processing to a separate thread that is managed by ASP.NET. We’ll look into threading later to understand what ASP.NET is doing. For now, ASP.NET receives this ECB reference and uses it internally to retrieve information about the current request. This includes such information as server variables, POST data, and output returning to the server. The ECB data block stays alive until the request finishes or times out in IIS. The ASP.NET engine continues to communicate with it until the request is done. Any output is written into the ISAPI output stream using the appropriate method call, and when the request is done, the ISAPI EXTENSIONISNOTIFIEDOFREQUESTCOMPLETION4HEEXTENSIONWILLTHENFREETHE%#"FROMMEMORY*UST REMEMBERTHATINTHISCRUELUNMANAGEDWORLDTHECODEISRESPONSIBLEFORHANDLINGALLIN MEMORY ACTIONS ANDNOTRELEASINGMEMORYLEADSTOMEMORYLEAKS(OWEVER THEIMPLEMENTATIONISVERYEFFI cient, as the .NET classes essentially act as a thin wrapper around ISAPI.

Loading the .NET Runtime Again, not much information about the loading procedure is available. I assume that the runtime is loaded, if not yet present, when the first request to ASP.NET is made by a mapped extension. The managed EO=LENqjpeia is then instantiated and starts talking to the unmanaged world. For isolation purposes, each virtual directory creates a new application domain (AppDomain). Within this App Domain the EO=LENqjpeia resides. Starting the application is also the beginning of the application’s life cycle, which we’ll look into later in the section called “The Life Cycles.” It’s also likely that the instantiation is made by the unmanaged part, because the wrapper interface is exposing the ?kiReoe^ha attribute. This makes it available from the other side. To create the ISAPIRuntime instance, the =ll@ki]ejB]_pknu*?na]pa method is called. The fol LOWINGCODESNIPPETIN,ISTING  CREATEDWITH2EFLECTOR SHOWSHOWITSDONEINTERNALLY Listing 1-3. The Code of the AppDomainFactory.Create Method Wnapqnj6I]nod]h=o$Qji]j]ca`Pula*Ejpanb]_a%Y lq^he_k^fa_p?na]pa$opnejc]llE`(opnejc]llL]pd% w k^fa_pk^f.7 pnu w eb$]llL]pdW,Y99#*#% w BehaEjbkejbk9jasBehaEjbk$]llL]pd%7 ]llL]pd9ejbk*BqhhJ]ia7 y eb$OpnejcQpeh*OpnejcAj`oSepd$]llL]pd(#XX#%% w ]llL]pd9]llL]pd'<X7 y EO=LE=llhe_]pekjDkop]llDkop9jasEO=LE=llhe_]pekjDkop$]llE`(]llL]pd(b]hoa%7 EO=LENqjpeiak9$EO=LENqjpeia%pdeo*[]llI]j]can*?na]paK^fa_pEjpanj]h$± ]llE`(pulakb$EO=LENqjpeia%(± ]llDkop(b]hoa(jqhh%7 k*Op]npLnk_aooejc$%7 k^f.9jasK^fa_pD]j`ha$k%7 y _]p_d$At_alpekj% w pdnks7 y napqnjk^f.7 y

C H A P T E R 1 N U N D E R S T A N D I N G A S P . N E T

Even if it is not visible in this code snippet, internally the appId is used to cache the relation with the requested virtual directory. Therefore subsequent calls do not start the application again, but process the existing =ll@ki]ej. Finally, in this code Op]npLnk_aooejc forces ISAPI to process the request, and, because it is asynchronous, the call returns immediately and the method returns the ECB as type k^fa_p, as shownIN&IGURE 

Figure 1-5. Behind the scenes, the first request is responsible for the creation of a new application.

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Handle the Request Within the Runtime The managed part is now alive, and ISAPI is able to call it whenever there is something available for processing. In basic ASP.NET terms, everything begins here. The AppDomain, the applica tion life cycle, and the first page cycle are born here and live for varying lengths of time. From now on, we’re back in the managed world. But there is a bit more you should know about the whole procedure. IIS is a multithreaded host and so is ISAPI. Each request is processed asynchronously, running in its own thread. Again, a look into the code using Reflector reveals what ASP.NET is doing here. The Lnk_aooNamqaop method receives an ISAPI ecb object and server type as parameters. The method is thread safe, so multiple ISAPI threads can safely call this single returned object instance simultaneously. lq^he_ejpLnk_aooNamqaop$EjpLpna_^(ejpeSNPula% w EjpLpnvank9EjpLpn*Vank7 eb$eSNPula99.% w vank9a_^7 a_^9Qjo]baJ]peraIapdk`o*CapA_^$vank%7 y EO=LESknganNamqaopsn9jqhh7 pnu w ^kkhqoaKKL9eSNPula99-7 sn9EO=LESknganNamqaop*?na]paSknganNamqaop$a_^(qoaKKL%7 sn*Ejepe]heva$%7 opnejc]llL]pdPn]joh]pa`9sn*Cap=llL]pdPn]joh]pa`$%7 opnejc]ll@ki]ej=llL]pdEjpanj]h9DpplNqjpeia*=ll@ki]ej=llL]pdEjpanj]h7 eb$$]ll@ki]ej=llL]pdEjpanj]h99jqhh% xxOpnejcQpeh*Amq]hoEcjkna?]oa$]llL]pdPn]joh]pa`(± ]ll@ki]ej=llL]pdEjpanj]h%% w DpplNqjpeia*Lnk_aooNamqaopJk@ai]j`$sn%7 napqnj,7 y DpplNqjpeia*Odqp`ksj=ll@ki]ej$± =llhe_]pekjOdqp`ksjNa]okj*Lduoe_]h=llhe_]pekjL]pd?d]jca`( ON*CapOpnejc$Dkopejc[Lduo[L]pd[?d]jca`(jask^fa_pWY± w]ll@ki]ej=llL]pdEjpanj]h(]llL]pdPn]joh]pa`y± %%7 napqnj-7 y _]p_d$At_alpekjat_alpekj% w ++naikra`bkno]gakb_h]nepu y y The code is just a part of the complete method. I have removed the catch block to focus on the working code. The method receives the pointer to an ECB data block and passes it to the ?na]paSknganNamqaop method. This method is responsible for creating the EO=LESknganNamqaop object. From now on there is a Namqaop object available that is able to talk directly to the ISAPI layer. The EO=LESknganNamqaop (defined in the Ouopai*Sa^*Dkopejc namespace) class is an abstract subclass of DpplSknganNamqaop4HISCLASSHOLDSALLTHEKNOWLEDGETOTALK(440)TSAPIECEOFCAKE and although it would take too much time to go into here, it’s worth a closer look if you like. I’d ENCOURAGEYOUTOGOONANDFINDOUTHOWTHINGSWORKUNDERTHEHOOD*USTOPENTHEMETHOD

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Lnk_aooNamqaop in Reflector, click on EO=LESknganNamqaop and then on the DpplSknganNamqaop subclass. At the end of the listing of signatures of either class, click on the link Expand Methods and there you have it. Since there is an abstract class, eventually there must be some implementation elsewhere. The factory method that creates the type using ?na]paSknganNamqaop method is able to return one of the following four types available:

s EO=LESknganNamqaopEjLnk_BknEEO3



s EO=LESknganNamqaopEjLnk_BknEEO2



s EO=LESknganNamqaopEjLnk_



s EO=LESknganNamqaopKqpKbLnk_

It’s a Bit in the ECB that drives the decision. This means that finally the ISAPI module controls the way ASP.NET handles requests. Because ASP.NET is not limited to IIS, it’s simply the version of IIS that is responsible for the factory’s selection. EO=LESknganNamqaopEjLnk_ type is for all IIS ver sions up to and including version 6, and EO=LESknganNamqaopEjLnk_BknEEO3type serves all versions FROMANDABOVE4HISSOUNDSSILLYˆTHEREISNO))3INEXISTENCEˆBUTTHE!30.%4ENGINEWOULD be robust against new versions as long as the ISAPI module is able to emulate IIS7 behavior. Whenever you have trouble understanding what is going on in your application, whether it’s with creating and sending headers, receiving weird stuff, or getting wrong data down the wire, it’s worth taking a closer look here. DpplSknganNamqaopISMEANTTOPROVIDEAHIGH LEVELABSTRACTIONAROUNDTHE LOW LEVELINTERFACES REGARDLESSOFTHESOURCEOFTHEDATA(OWEVER READINGANDUNDERSTANDINGARETWO different things. Let’s take an example of how to deal with all the internals. The next listing shows you HOWTHEWELL KNOWN1UERY3TRINGISRETRIEVEDFROMTHE%#"-OVINGDOWNTHECLASSHIERARCHY YOULL find that it’s partly implemented in the base class and partly in the EO=LESknganNamqaopEjLnk_ class. For IIS6 and IIS7 there is no distinct change here, so you can skip these classes for now. ejpanj]hkranne`aejpCapMqanuOpnejcN]s>upao?kna$^upaWY^qbban(ejpoeva% w eb$^]oa*[a_^99EjpLpn*Vank% w napqnj,7 y napqnjQjo]baJ]peraIapdk`o*A_^CapMqanuOpnejcN]s>upao$^]oa*[a_^(^qbban(oeva%7 y W@hhEilknp$sa^ajceja*`hh%Y ejpanj]hop]pe_atpanjejpA_^CapMqanuOpnejcN]s>upao$EjpLpnlA?>(^upaWY^qbban(± ejpoeva%7 Again, nothing is thrilling here. These classes are all very thin wrappers around native method calls. In fact, ASP.NET does not provide any significant overhead to the request procedure. That MEANS!30.%4ISEXTREMELYFASTˆASFASTAS))3WITHNATIVECODE)FYOUFEELORKNOW THATYOUR application is slow, then you know that in most cases it will be a problem in your code. Let’s focus on the managed side of the world and learn more about what’s going on here.

HttpContext and HttpApplication You’re probably already familiar with the Dppl?kjpatp and Dppl=llhe_]pekj classes. Instances of these classes are created whenever a request hits the engine. At a glance, the steps are:

s #REATEANEWDppl?kjpatp instance for the request.



s 2ETRIEVEANDppl=llhe_]pekj instance (or create one, if it’s the first request).



s #ALLDppl=llhe_]pekj*Ejep to set up pipeline events.



s #ALLDppl=llhe_]pekj*NaoqiaLnk_aooejc to start the ASP.NET pipeline processing.

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Wrapping the Request: HttpContext 4HECONTEXTOFAN(440REQUESTISAVAILABLETHROUGHOUTTHELIFETIMEOFTHEREQUEST&OREASEOFUSE it’s always accessible through the static Dppl?kjpatp*?qnnajp property. Because every request usu ally starts a new thread, or recycles a free one from the thread pool, your code runs in that thread. In Chapter 2 I’ll explain in more detail the thread and processing behavior. For now, this isn’t needed TOUNDERSTANDTHEREQUESTPROCESSINGONTHECONTEXTLEVEL4HECURRENTCONTEXTHASAONE TO ONE relation to the request for that thread. This context object is also the place where all other objects required to process the request are stored: Namqaop, Naolkjoa, =llhe_]pekj, Oanran, and ?]_da. At any time during request processing Dppl?kjpatp*?qnnajp gives you access to all these. There are several shortcuts, so you may use the Page’s property ?kjpatp instead, but it’s exactly the same object. You may already use several collections available in the =llhe_]pekj, Oaooekj, and ?]_da objects. Even the Dppl?kjpatp class contains a useful collection that provides a store for request spe cific data. The big difference to the other data collections is the life time. The Dppl?kjpatp represents exactly the current request. If the processing is finished and the data sent to the server, which in TURNSENDSITBACKTOTHECLIENT THENTHECOLLECTIONSAREALSODISPOSEDOF(OWEVER THE#ONTEXTEXISTS before the page’s life span begins and ends after it finishes. Technically it’s an object and it ends when it gets disposed. This data storage is therefore a bit more powerful than simple page members. ,ISTING SHOWSHOWTOUSE?kjpatp*Epaio to get information about the request processing elapsed time. At the >acejNamqaop event a timestamp is stored and retrieved later at Aj`Namqaop. Both events are part of the page’s life cycle and are explained in more detail later in the section “The Page’s Life Cycle.” Listing 1-4. Get Request Information Using Events in global.ascx =llhe_]pekj[>acejNamqaop$k^fa_poaj`an(Arajp=ncoa% w eb$Oappejco*@ab]qhp*Hkccejc% w ?kjpatp*Epaio*=``$HkcPeia(@]paPeia*Jks%7 y y lnkpa_pa`rke`=llhe_]pekj[Aj`Namqaop$k^fa_poaj`an(Arajp=ncoa% w eb$Oappejco*@ab]qhp*Hkccejc% w @]paPeiaaj`9@]paPeia*Jks7 PeiaOl]jol]j9aj`*Oq^pn]_p$$@]paPeia%?kjpatp*EpaioWHkcPeiaY%7 Ouopai*@e]cjkope_o*@a^qc*SnepaHeja$ol]j*Pkp]hIehheoa_kj`o(NamqaopPeia%7 y y This sample uses two events defined in the global.ascx code behind file. You might be thinking of how to put the results into a database or log file, but for now the output to a Visual Studio console WINDOWWILLDOSEE&IGURE   If you feel that the values shown in the figure are too high, you need to be aware that I’m run ning the entire environment in a Virtual PC console, and that the timestamps shown are expressed in milliseconds.

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Figure 1-6. Get time information about the request while debugging.

The Core Type: HttpApplication The Dppl=llhe_]pekjB]_pknu is responsible for creating an appropriate number of Dppl=llhe_]pekj objects. The load and the number of threads required affect how it handles incoming requests. The size of the pool is limited to the I]tSknganPdna]`o setting in the Lnk_aooIk`ah key in the machine. config WHICHBYDEFAULTIS3INCETHEDAYSOF.%4ITSSTILLANAUTO CONFIGUREDENTRY 8lnk_aooIk`ah]qpk?kjbec9pnqa+: Change this to the following: 8lnk_aooIk`ah]qpk?kjbec9b]hoai]tSknganPdna]`o9/,+: You can find more information about threading in Chapter 2. 4HEPOOLSTARTSOUTWITHASMALLERNUMBERˆUSUALLYONEˆANDITTHENGROWSASMULTIPLESIMUL taneous requests are processed. The pool is monitored so that under load it grows to a maximum number of instances. Later the pool is scaled back to a smaller number as the load drops. Once you have the right number of instances of Dppl=llhe_]pekj, you have the real entry point within the managed world for an incoming request. Dppl=llhe_]pekj is like an outer container for the whole application. For easy access the events related to the application are mapped in the global.asax file, which is the declarative expression of this class. This is true for all mapped requests handled by ASP.NET handlers. Other requests might be handled inside custom modules but would not appear in global.asax when running IIS7 integrated mode. The definition of global.asax in global.asax.cs reveals: lq^he__h]ooChk^]h6Ouopai*Sa^*Dppl=llhe_]pekj During each request handling in the ASP.NET pipeline, several events let you control and INTERCEPTTHEVARIOUSSTATESOFTHEAPPLICATIONSLIFECYCLE,ISTING SHOWSALLOFTHEM EVENIFTHE majority is never used in an application. In the next few sections, I’ll dig deeper into the world of application events. Listing 1-5. Events Available on Application Level (Pulled from HttpApplication) lq^he_arajpArajpD]j`han>acejNamqaop7 lq^he_arajpArajpD]j`han=qpdajpe_]paNamqaop7 lq^he_arajpArajpD]j`hanLkop=qpdajpe_]paNamqaop7 lq^he_arajpArajpD]j`han=qpdknevaNamqaop7 lq^he_arajpArajpD]j`hanLkop=qpdknevaNamqaop7 lq^he_arajpArajpD]j`hanNaokhraNamqaop?]_da7 lq^he_arajpArajpD]j`hanLkopNaokhraNamqaop?]_da7 lq^he_arajpArajpD]j`hanI]lNamqaopD]j`han7 lq^he_arajpArajpD]j`hanLkopI]lNamqaopD]j`han7

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lq^he_arajpArajpD]j`han=_mqenaNamqaopOp]pa7 lq^he_arajpArajpD]j`hanLkop=_mqenaNamqaopOp]pa7 lq^he_arajpArajpD]j`hanLnaNamqaopD]j`hanAta_qpa7 lq^he_arajpArajpD]j`hanLkopNamqaopD]j`hanAta_qpa7 lq^he_arajpArajpD]j`hanQl`]paNamqaop?]_da7 lq^he_arajpArajpD]j`hanLkopQl`]paNamqaop?]_da7 lq^he_arajpArajpD]j`hanHkcNamqaop7 lq^he_arajpArajpD]j`hanLkopHkcNamqaop7 lq^he_arajpArajpD]j`hanAj`Namqaop7 lq^he_arajpArajpD]j`han@eolkoa`7 lq^he_arajpArajpD]j`hanAnnkn7 lq^he_arajpArajpD]j`hanLkopNaha]oaNamqaopOp]pa7 lq^he_arajpArajpD]j`hanLnaOaj`Namqaop?kjpajp7 lq^he_arajpArajpD]j`hanLnaOaj`NamqaopDa]`ano7 lq^he_arajpArajpD]j`hanNaha]oaNamqaopOp]pa7 "YWRITINGSOMETHINGLIKETHEFOLLOWINGINTOTHECODE BEHINDFILE YOUATTACHANEVENTTOALL requests against the dedicated handler: lnkpa_pa`rke`=llhe_]pekj[>acejNamqaop$k^fa_poaj`an(Arajp=ncoa% Avoiding an explicit delegate definition is just for the sake of convenience. The whole handling of =ll@ki]ej, Dppl=llhe_]pekj, and threads might look confusing. Remember that the server has to handle multiple incoming requests simultaneously. Each ASP. NET application runs in its own AppDomain, where several instances of Dppl=llhe_]pekj can run in parallel, supplied from the pool managed by the factory. To get a better understanding of this, let’s EXAMINETHEINFORMATIONYOUCANEXTRACTFROMRELATEDOBJECTS*USTTOCLARIFYTYPICALUSAGESCENARIOS THEFOLLOWINGCODESAMPLESRUNON))3 BASEDSYSTEMSONLY/THER7EB3ERVERSDOESNOTSUPPORT application pools. )N,ISTING  THEVALUESAREWRITTENINTOH]^ah controls named appId, threadId, domainId, threadInfo, and threadApart2EFERTO&IGURE TOSEETHEOUTPUT Listing 1-6. Retrieving Information About the Application (Excerpt) lnkpa_pa`rke`L]ca[Hk]`$k^fa_poaj`an(Arajp=ncoa% w Cqe`e`9$Cqe`%=llhe_]pekjW=llE`Y7 pdeo*]llE`*Patp9e`*PkOpnejc$%7 pdeo*pdna]`E`*Patp9Pdna]`*?qnnajpPdna]`*I]j]ca`Pdna]`E`*PkOpnejc$%7 pdeo*`ki]ejE`*Patp9=ll@ki]ej*?qnnajp@ki]ej*Bneaj`huJ]ia7 pdeo*pdna]`Ejbk*Patp9Pdna]`*?qnnajpPdna]`*EoPdna]`LkkhPdna]`;± LkkhPdna]`6JkPdna]`7 pdeo*pdna]`=l]np*Patp9Pdna]`*?qnnajpPdna]`*Cap=l]npiajpOp]pa$%*PkOpnejc$%7 Pdna]`*Ohaal$0,,,%7 y The Ohaal call allows you to open several browser instances and hit F5 to refresh the page WITHINTHEFOUR SECONDPERIODINORDERTOSEEHOWITWORKS4HISSIMULATESTHEBEHAVIORWHENSEV eral requests come in while previous requests are still running. An application by definition has no internal id. To create one, add the following code to the global.asax code behind: rke`=llhe_]pekj[Op]np$k^fa_poaj`an(Arajp=ncoa% w =llhe_]pekjW=llE`Y9Cqe`*JasCqe`$%7 y

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&IGURE SHOWSTHREESCREENSMADEWITHINTHEFOUR SECONDPERIODUSINGTHREEDIFFERENT browser windows.

Figure 1-7. The application’s id changes as the thread id does. You can see that the application id and the thread id change. If you remove the Ohaal com mand and request the pages one by one, the application id is always the same. Usually the thread is recycled from the pool and the id is also unchanged. The abbreviation ‘MTA’ for the thread’s apartment model stands for Multi Threaded Apart ment. You can override this apartment state in ASP.NET pages with the =ol?kil]p9pnqa attribute in the
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Flowing Through the ASP.NET Pipeline You now have a good overview of what happens when a request comes in, and of how the (TTP#ONTEXTAND(TTP!PPLICATIONOBJECTSSTARTUPASTHEYWAITTOBEUSEDINYOURCODE4HEREARE several steps following this startup sequence worth investigating further. In each step, you’ll find events and callbacks to intercept the process and customize or optimize its behavior. &IGURE ILLUSTRATESWHATHAPPENSDURINGTHEVARIOUSSTATES)FYOULOOKINTOTHECODEUSING Reflector, you can find the steps in subclass =llhe_]pekjOpalI]j]can and the additional steps for IIS7 in LelahejaOpalI]j]can.

Figure 1-8. Events that build the pipeline The most important information here is that modules precede handlers. Modules are respon sible for all requests, whereas handlers support a specific extension, like &*]olt. You can find an IN DEPTHEXPLANATIONABOUTBOTHMODULESANDHANDLERSIN#HAPTER4OHAVEABRIEFOVERVIEW LETSRECALLTHEWAY!30.%4HANDLESEACHREQUESTTHROUGHTHEPIPELINE-ODULESAND(ANDLERS are the two processing points of this pipeline. Modules are just like a filter. The modules are called before and after the handler executes. Examples for related events in the pipeline are BeginRequest, AuthenticationRequest event, EndRequest event, etc. You may intercept, participate, and modify each request. Despite this, you may think of it as a program that executes some code for the request.

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An .aspx page can be thought of as a handler, which implements specific functions. They are loaded and executed at the particular state of the processing pipeline, if configured properly in web.config file. The figure shows only the minimum number required to execute a page. You’ll find a closer look at all these events in the next section. For now, it’s enough to know when and why the modules and handlers get executed. This is the major part of the pipeline business, which I’ll also discuss in the next section.

Modules and Handlers Using HttpModule and HttpHandler Dppl=llhe_]pekj and Dppl?kjpatp are merely containers for incoming messages. They build the pipeline by forming a chain of events that commence in a defined order, and they hold together data related to the request in order to give other instances easy access to the information involved in the PROCESS(OWEVER THEREALWORKISDONEINOTHERPROCESSINGUNITS PARTICULARLYTHEMODULESANDHAN dlers. Modules are built on top of the DpplIk`qhaCLASS(ANDLERSAREBUILTONTOPOFTHEDpplD]j`hano class. Both are abstract classes and need concrete implementations. In addition, both are highly configurable and act as a chain of instances. This means that you can attach as many modules and handlers as you like and the request will flow through all of these instances. 3EVERALTASKSCOULDBEHANDLEDINBOTHLEVELSˆHOWEVER THEREISADIFFERENTINTENTIONBEHIND THEM-ODULESTENDTOCONTROLTASKSONALOWERLEVELTHEIRNATUREISMOREBASICTHANTHATOFHAN dlers. Think of modules as the right place to prepare data being processed by handlers or modify data subsequently when the regular treatment by a handler is completed. IIS programming aficio nados can think of modules as ISAPI filters. The good news is that programming ASP.NET modules using .NET is much easier than developing filters for IIS. Moving on from IIS, let’s focus on the amazing things that become possible as ASP.NET is extended. The natural order of modules and handlers is: 1. 5SEMODULETOPRE PROCESSAREQUEST 2. Use handler to process the request. 3. 5SEMODULEAGAINTOPOST PROCESSTHEREQUEST ASP.NET comes with several default handlers, such as the very basic ones for &*]oltpages or Web Services. Some default modules exist that are responsible for simple tasks like authentication and caching. In an ideal world, the modules are transparent to the handlers. This means that han dlers don’t know about the modules that work before or after their own processing. ASP.NET allows several easy ways to create your own modules and handlers. This is usually the first approach of extending the standard behavior of ASP.NET. Let’s take ACLOSERLOOKATTHISTECHNIQUE&IGURE SHOWSHOWMODULESANDHANDLERSFITINTOTHE!30.%4 process model. In Chapter 3, I’ll discuss the process of developing custom modules and custom handlers with some clever examples. By now it’s enough to know that several modules process the request one after another on both the request and the response path. Whereas only one handler processes the request finally, it’s either an internal handler or a custom one. (OWEVER ALLTHESETECHNIQUESAREBASEDONTHEBEHAVIOROFTHEPIPELINE4HISPIPELINEFIRESTHE events that form theSO CALLEDLIFECYCLES

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Figure 1-9. Modules and handlers fit closely in the ASP.NET model.

The Life Cycles The life cycle is a term used in almost every introduction to ASP.NET. This term is absolutely crucial for a complete understanding and the correct usage of ASP.NET. To break things down let’s divide the different life cycles into three parts:

s 4HEAPPLICATIONSLIFECYCLE



s 4HEPAGESLIFECYCLE



s 4HECONTROLSLIFECYCLE

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4HEFOLLOWINGSECTIONSCOVERTHISIN DEPTH4HEBEHAVIOROFTHECYCLESISSLIGHTLYDIFFERENT between IIS versions, but the overall description is the same. The following explanations focus on ))3AND&RAMEWORKBEHAVIOR WHICHISVALIDFOR.%4UPTOTHEUPCOMING IIS7 can run in two different modes. The IIS integrated mode is the new native one, whereas the classic mode mimics the behavior of IIS5 or IIS6. The integrated mode has several advantages and should be preferred if there is no explicit requirement to step down.

IIS7 Integrated Pipeline The IIS7 integrated pipeline is a unified request processing pipeline. Each incoming request is handled by this pipeline and routed through the internal parts of IIS. The pipeline supports both managed and native code modules. You may already know about creating managed modules based on the EDpplIk`qha interface. Once implemented and hooked into the pipeline, the module receives all events used to interact with the request passing through the pipe. The term “unified request processing pipeline” needs some more investigation. IIS6 provided two different pipelines: one for native and one for managed code. This is obviously for historical rea sons, because the managed world came after the IIS world. In IIS 7 both pipelines united to become the unified request processing pipeline. For ASP.NET developers this has several benefits:

s 4HEINTEGRATEDPIPELINERAISESALLEXPOSEDEVENTS WHICHENABLESEXISTING!30.%4MODULES to work in the integrated mode.



s "OTHNATIVE CODEANDMANAGED CODEMODULESCANBECONFIGUREDATTHE7EB3ERVER 7EB site, or Web application level.



s -ANAGED CODEMODULESCANBEINVOKEDATCERTAINSTAGESINTHEPIPELINE



s -ODULESAREREGISTEREDANDENABLEDORDISABLEDTHROUGHANAPPLICATIONSWeb.config file.

4HECONFIGURATIONOFMODULESINCLUDESTHEBUILT IN!30.%4MANAGED CODEMODULESFORSES SIONSTATE FORMSAUTHENTICATION PROFILES ANDROLEMANAGEMENT&URTHERMORE MANAGED CODE modules can be enabled or disabled for all requests, regardless of whether the request is for an ASP. NET resource like an *]olt file or a static file like an image. Invoking modules at any stage means that this may happen before any server processing occurs for the request, after all server processing has occurred, or anywhere in between.

The Application’s Pipeline In more generic terms the pipeline describes the flow through several instances within the IIS. Each step processes the request in a distinct way and fires appropriate events. This forces inter actions with the modules and applications attached by configuration. The variety of actions you CANPERFORMRANGESFROMNONETOTOTALCONTROL(OWEVER DOINGNOTHINGLETSTHEBUILT INMODULES accomplish their job and handle the basic page processing. From the perspective of the extensibil ITYOF!30.%4 hTOTALCONTROLvISWHATWERELOOKINGFOR&IGURE SHOWSTHEAPPLICATIONLIFECYCLE events.

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Figure 1-10. Application’s life cycle events 4WOSTATESARENEWIN))3-AP(ANDLER and Log Request. This gives developers much more control over the request process. Some modules are managed, whereas others are written in native CODE9OUCANADDYOUROWNMODULESINEITHERWAY(OWEVER ASA.%4DEVELOPER YOUDPROBABLY prefer writing in managed code and I would strongly recommend this. (Native code is an option if YOUNEEDTOCREATEAHIGH PERFORMANCEMODULE which performs simple functions.)

The Request Arrives The application life cycle begins when a request is made for an application resource sent by a client application, such as a browser, to the Web Server. In integrated mode, the unified pipeline handles all requests. When the pipeline receives a request, it’s being passed through stages that are common to all requests. These stages are represented internally by the NamqaopJkpebe_]pekj enumeration. The enumeration is defined in the Ouopai*Sa^ namespace. All request stages can be configured to

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allow developers to take advantage of ASP.NET functionality. That functionality is encapsulated in M ANAGED CODEMODULESTHATHAVEACCESSTOTHEREQUESTPIPELINE&ORINSTANCE EVENTHOUGHTHEHTM FILENAMEEXTENSIONISNOTMAPPEDBYDEFAULTTO!30.%4 AREQUESTFORAN(4-,PAGESTILLINVOKES ASP.NET modules. This enables you to take advantage of ASP.NET authentication and authorization for all resources.

Unified Pipeline Receives the First Request When the unified pipeline receives the first request for any resource in an application, an instance of the =llhe_]pekjI]j]can class is created. Its core function is to build the application domain (AppDomain) in which the request is processed. Application domains provide isolation between applications for global variables and enable each application to be unloaded separately. In the application domain, an instance of the DkopejcAjrenkjiajp class is created, which provides access to information about the application, such as the name of the folder where the application is stored. You can find both types in the Ouopai*Sa^*Dkopejc namespace. The first request has several additional tasks. You will notice this because the elapsed time for THEPAGETOBEDELIVEREDISLONGERTHANALLSUBSEQUENTREQUESTS$URINGTHEFIRSTREQUEST TOP LEVEL items in the application are compiled, if required. This includes application code in the project. By THEWAY SINCETHEDAYSOF6ISUAL3TUDIO THEREISNOLONGERASPECIALCODEFOLDERNAMED!PP? Code. Even if you name a folder this, it will have no special function. Code that resides in any folder at any level is compiled in one assembly per project.

Response Objects Are Created for Each Request After the application domain has been created and the DkopejcAjrenkjiajp object has been instan tiated, application objects such as Dppl?kjpatp, DpplNamqaop, and DpplNaolkjoa are created and initialized. These objects exist throughout the lifetime of the request and give developers full access to all related data. The Dppl?kjpatp class contains objects that are specific to the current application request, such as the DpplNamqaop and DpplNaolkjoa objects. The DpplNamqaop object contains information about the current request, which includes cookies and browser information. The DpplNaolkjoa object contains the response that is about to be sent to the client, which includes all rendered output and header data, such as cookies. Dppl?kjpatp*?qnnajp gives you permanent access to the current con text through a static method. For easy access the L]ca class has properties like Namqaop and Naolkjoa that return instances of the very same related objects.

Differences Between IIS6 and IIS7 We’re currently in the transition period from IIS6 to IIS7. While IIS7 is the best choice for a Web Server on Microsoft platforms, there are still many servers with IIS6 in production. Because you may already have a deep understanding of processing ASP.NET based on IIS6, the following explanation focuses on the key differences between IIS6 and IIS7, running in both Integrated mode and with the .NET Framework 3.5 or later. The following properties are specific to IIS7 with Integrated mode. You must run IIS7 to take advantage of the following features. The DpplNaolkjoa object has a new property Oq^Op]pqo?k`a. This is useful for setting codes for tracking failed requests. The Da]`ano property of the DpplNaolkjoa object provides access to response headers for the response. Two properties of the Dppl?kjpatp object, EoLkopJkpebe_]pekj and ?qnnajpJkpebe_]pekj, are used when one event handler handles several Dppl=llhe_]pekj events. This might happen when you try to simplify your code and use a osep_H BLOCKTODISTINGUISHBETWEENCON crete events. ?qnnajpJkpebe_]pekj returns a value from enumeration NamqaopJkpebe_]pekj. This enum does not have specific values for the post events. To recognize the post event just read the Boolean value from EoLkopJkpebe_]pekj.

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Both the Da]`ano and OanranR]ne]^hao property of the DpplNamqaop objectAREWRITE ENABLED

An HttpApplication Object Is Assigned to the Request After all application objects have been initialized, the application is started by creating an instance of the Dppl=llhe_]pekj class. If the application has a chk^]h*]o]t file, ASP.NET instead creates an instance of the chk^]h*]o]t class that is derived from the Dppl=llhe_]pekj class. It then uses the derived class to represent the application. This way you get access to the application events simply by overwriting the handlers within the chk^]h*]o]t code portion.

NNote

The first time that an ASP.NET page or process is requested in an application, a new instance of the

Dppl=llhe_]pekj class is created. However, to maximize performance, Dppl=llhe_]pekj instances might be

reused for multiple requests.

Request Is Processed by the Pipeline The Dppl=llhe_]pekj class performs several tasks while the request is being processed. Each step fires a specific request to allow you to run code when the event is raised. Without any further action, all incoming requests will fire all events and the attached modules will be invoked in sequence. To take advantage of extensibility, some interfaces come into the scope. EDpplIk`qha is the basic inter face for custom modules. In IIS7’s integrated mode you can use the module’s Ejep method to attach the required events. One step you’re supposed to perform is the request validation. Imagine hackers trying to send malicious markup or other intrusions. The following list of events shows all steps you can run pri vate code in. Validating the request should take place as early as possible, according to the following list in >acejNamqaop.

s 2AISETHE>acejNamqaop event.



s 2AISETHE=qpdajpe_]paNamqaop event.



s 2AISETHELkop=qpdajpe_]paNamqaop event.



s 2AISETHE=qpdknevaNamqaop event.



s 2AISETHELkop=qpdknevaNamqaop event.



s 2AISETHENaokhraNamqaop?]_da event.



s 2AISETHELkopNaokhraNamqaop?]_da event.



s 2AISETHEI]lNamqaopD]j`han event. An appropriate handler is selected based on the file name extension of the requested resource. The handler can be a native code module, such as the IIS7 Op]pe_BehaIk`qha( or a managed module, such as the L]caD]j`hanB]_pknu class.



s 2AISETHELkopI]lNamqaopD]j`han event.



s 2AISETHE=_mqenaNamqaopOp]pa event.



s 2AISETHELkop=_mqenaNamqaopOp]pa event.



s 2AISETHELnaNamqaopD]j`hanAta_qpa event. Call either the Lnk_aooNamqaop method for syn chronous calls or the asynchronous version EDppl=ouj_D]j`han*>acejLnk_aooNamqaop of the appropriate EDpplD]j`han class.



s 2AISETHELkopNamqaopD]j`hanAta_qpa event.



s 2AISETHENaha]oaNamqaopOp]pa event.

C H A P T E R 1 N U N D E R S T A N D I N G A S P . N E T



s 2AISETHELkopNaha]oaNamqaopOp]pa event.



s 0ERFORMRESPONSEFILTERINGIFTHEBehpan property is defined.



s 2AISETHEQl`]paNamqaop?]_da event.



s 2AISETHELkopQl`]paNamqaop?]_da event.



s 2AISETHEHkcNamqaop event.



s 2AISETHELkopHkcNamqaop event.



s 2AISETHEAj`Namqaop event.



s 2AISETHELnaOaj`NamqaopDa]`ano event.



s 2AISETHELnaOaj`Namqaop?kjpajp event.

The Page’s Life Cycle After understanding the application’s life cycle, you’re now ready to move further along the path taken by the request. The request is now being processed until the resources are prepared and ready TOBESERVED&ORSTATICRESOURCESITSEASYTHEDATAISALLREADYTOSENDTOTHECLIENT%XAMPLESOF STATICRESOURCESINCLUDEIMAGES *AVA3CRIPTFILES ANDEMBEDDEDOBJECTS 4HEMOREEXCITINGINFOR mation is how dynamic resources are processed. The basic steps in the page’s life cycle include initialization, instantiating controls, restoring and maintaining state, running event handler code, and rendering. As you saw in the application’s life cycle, you will be able to interact with the processing and change the handling for your intended effects. Some steps during the page’s life cycle are more complex and require a closer look in order to take full advantage of their customization potential. One major portion is the view state handling. I’ll dedicate a whole section to explaining view state later in section “View State.” It is also important for you to understand the page life cycle. As a developer creating custom controls, for instance, you must be familiar with the life cycle in order to correctly initialize controls, populate control properties with view state data, and run any control behavior code. You may have heard of a control life cycle, too. You may already know that a page in ASP.NET is a sort of special IZEDCONTROL ANDTHEREFOREACONTROLSLIFECYCLEISVERYSIMILAR(OWEVER PAGESHAVEMORE events available.

NTip When an application operates in the context of Visual Studio while you run a debug session, the application starts with the launch of the integrated Web Server. When the debug session ends and you launch the application again using the F5 key, the integrated Web Server will run the same application domain. This means that between the debug sessions no new application life cycle is being started. To force the application to restart you can right click the notification icon in the system tray and stop the Web Server.

What About Master Page Life Cycle? You might miss information regarding master pages here. The master page itself does not have any stages, because it’s not an object created and run standalone. The master page hierarchy is used to resolve the final construct of the page requested, and then the page’s life cycle begins. Therefore, the master page is treated like a control, with some events related to the page’s life cycle events, but again, not with its own life cycle.

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Page Request Stages The page request occurs before the page life cycle begins. When the page is requested by a client, ASP.NET determines whether the page needs to be parsed and compiled, or whether a cached ver sion of the page can be sent in response without executing the page. In each case the “life” of the page begins.

Start In this step, page properties such as Namqaop and Naolkjoa are set. These properties give you access to the current DpplNamqaop and DpplNaolkjoa instances created through the application’s life cycle. You can access all information related to the request using pdeo*Namqaop* (In later stages you can modify the response created and stored in pdeo*Naolkjoa.) At this stage, the page also deter mines whether the request is a postback or a new request and sets the EoLkop>]_g property. This involves two checks: whether the request is done as a POST, and whether it comes from the same ASP.NET page. Additionally, during the Start step, the page’s QE?qhpqna property is set. At this point you can perform any action based on the automatically recognized page culture. Alternatively, you can force the culture property, so that the correct resources are obtained. (Forcing the culture doesn’t work in other steps.)

Page Initialization During page initialization step, controls on the page become available and each control’s QjemqaE@ property is set. The QjemqaE@ is used later on postbacks to assign control state in order to make forms sticky. Any themes are also applied to the page. If the current request is a postback, the post back data has not yet been loaded and control property values have not been restored to the values from view state.

Load During load, if the current request is a postback, control properties are loaded with information recovered from view state and control state. For a regular request via GET, view state and control state are set to their respective default states.

Validation During this step the R]he`]pa method of all validator controls is called. The EoR]he` property of all validator controls is set, and as a summary the page’s EoR]he` property is set, too.

Postback Event Handling If the request is a postback, any event handlers are called, such as button click events.

Rendering Before rendering, view state is saved for the page and all controls. Rendering is the process that CREATESTHE(4-,THATMAKESTHEPAGEVISIBLEINABROWSER%ACHCONTROLISRESPONSIBLEFORRENDER INGITSELF4HISFEATUREANDTHEEXTENSIBLEDESIGNTIMESUPPORTISAMAJOROPPORTUNITYFORTHIRD PARTY control vendors. Their controls can encapsulate all the clever design time experience and runtime functionality within each control. That means during the rendering phase, the page calls the Naj`an method for each control, providing a PatpSnepan instance that writes its output to the KqplqpOpna]i of the page’s Naolkjoa property.

C H A P T E R 1 N U N D E R S T A N D I N G A S P . N E T

Unload Unload is called after the page has been fully rendered, sent to the client, and is ready to be dis carded. At this point, page properties such as Naolkjoa and Namqaop are unloaded and any cleanup is performed.

Events Fired Within the Life Cycle’s Stages Within each stage of the life cycle of a page, the page raises events that you can handle to run your own code. For control events, you bind the event handler to the event, either declaratively using attributes such as kj_he_g, or in code. When inheriting a class from the L]ca class, you can override methods from the page’s base class. It’s a common technique to create your own base page classes that derive from L]ca and to handle common tasks there. For example, you can override the page’s Ejepe]heva?qhpqna method to dynamically set culture information. Overriding event handlers or attaching events are two different methods to perform almost the same action. If you use the Page_<event> syntax, you don’t need to HANDLETHEBASEIMPLEMENTATION(OWEVER IFYOUOVERRIDETHEMETHODYOUMUSTHANDLETHEBASE implementation and therefore call the base method. You can do this at the beginning, at the end, or anywhere in between. Despite this, a regular attach event handler can be used as well. Additionally, the =qpkArajpSenaql attribute of signature already mentioned. 0AGESALSOSUPPORTAUTOMATICEVENTWIRE UP MEANINGTHAT!30.%4LOOKSFORMETHODSWITH particular names and automatically runs those methods when certain events are raised. If the =qpkArajpSenaql attribute of the , such as L]ca[Hk]` and L]ca[Ejep. The following sections list all the page events. Some events that do not map directly to the cor RESPONDINGSTAGESARELESSCRUCIALBUTGIVEYOUMORECONTROLFROMTHEEXTENSIBILITYPERSPECTIVEˆFOR example, when you create custom controls that require a very specific behavior.

PreInit Event Use this event to check the EoLkop>]_g property to determine whether this is the first time the page ISBEINGPROCESSED#REATEORRE CREATEDYNAMICCONTROLS9OUMAYALSOSETMASTERPAGESANDTHE Pdaia property dynamically. Read or set any profile property values. If the request is a postback, the values of the controls have not yet been restored from view state during LnaEjep state. If you set a control property at this stage, its value might be overwritten in the next event.

Init Event This event is raised after all controls have been initialized and any skin settings have been applied. Use this event to read or initialize control properties.

InitComplete Event This event is raised by the Page object. Use this event for processing tasks that require all initializa tion be complete.

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PreLoad Event Use this event if you need to perform processing on your page or control before the Load event. Before the Page instance raises this event, it loads view state for itself and all controls, and then processes any postback data included with the Namqaop instance.

Load Event The Page calls the KjHk]` event method on the L]ca, then recursively does the same for each child control, which does the same for each of its child controls until the page and all controls are loaded. Use the overridden KjHk]` event method to set properties in controls and establish database connections. In a postback request during Hk]` event, if the page contains validator controls, check the EoR]he` property of the L]ca and of individual validation controls before performing any processing.

Control events After Load the control events occur. Use these events to handle specific control events, such as a Button control’s Click event or a TextBox control’s TextChanged event.

LoadComplete Event Use this event for tasks that require all other controls on the page be loaded.

PreRender Event Before this event occurs, the L]ca object calls Ajoqna?deh`?kjpnkho for each control and for the page itself. Each data bound control whose @]p]Okqn_aE@ property is set calls its @]p]>ej` method. The LnaNaj`an event occurs for each control on the page. Use the event to make final changes to the con tents of the page or its controls. 4HERENDERPROCESSITSELFDOESNOTHAVEANEVENTITHAPPENSAFTERLnaNaj`an and before QjHk]` and can be intercepted by overwriting the Naj`an method.

SaveStateComplete Event Before this event occurs, view state has been saved for the page and for all controls. Any changes to the page or controls at this point will be ignored. See the section about view state later in this chap ter to learn more about its specific behavior. Use this event to perform tasks that require view state to be saved, but that do not make any changes to controls.

Unload Event This event occurs for each control and, when all control events are done, for the page. In controls, use this event to do final cleanup for specific actions, such as closing database connections. For the page itself, use this event to do final cleanup work, such as closing open files and database connec TIONS FINISHINGUPLOGGINGOROTHERREQUEST SPECIFICTASKS During the Qjhk]` stage, the page and its controls have been rendered, so you cannot make further changes to the response stream. If you attempt to call a method, such as the Naolkjoa*Snepa method, the page will throw an exception.

C H A P T E R 1 N U N D E R S T A N D I N G A S P . N E T

Additional Page Life Cycle Considerations Server controls have their own life cycle that is similar to the page life cycle. A control’s Ejep and Hk]` events occur during the corresponding page events. Due to the hierarchical nature of the page’s controls, this happens recursively. For the event order this means in turn the events appear in reverse order. This is clearly the expected behavior, because the Ejep event on page level indicates that all subsequent EjepEVENTSARECOMPLETED9OUMAYREADTHEEVENTASh)S)NITIALIZEDv(OW ever, the Hk]` event for a container occurs before the Hk]` events for its child controls, which is the opposite behavior. This is so that you can have access to the process before any other processing takes place. From the perspective of the Ejep event, it doesn’t make sense to do anything before it appears, because there is nothing you can access in your code. You can change the properties of a control by handling the events for the control, such as the ?he_g event for the >qppkj control. Control events appear after the page’s Hk]` event has been fired.

Dynamic Controls and Data Binding Events The page and control life cycles define a chain of events to give you maximum control over the cre ATIONANDRUNTIMEOFTHECONTROL(OWEVER THECONTROLHANDLINGHASMOREPOSSIBILITIESTHANYOUCAN achieve with such a straightforward model. You will see a different behavior when adding controls DYNAMICALLY&URTHERMORE DATA BOUNDCONTROLSWORKINTERNALLYSLIGHTLYDIFFERENTDUETOTHEWAY data templates are parsed and executed.

Dynamic Control Events The page life cycle and control life cycle are very similar because of the nature of a L]ca as a class derived from ?kjpnkh(OWEVER YOUCANADDCONTROLSDYNAMICALLYˆAFEATUREWHICHDOESNTMAKE SENSEFORPAGES9OUMIGHTASSUMETHATADDINGCONTROLSISNOTVERYCOMMONIN!30.%4(OWEVER IMAGINETHATDECLARATIVELYAUTHOREDCONTROLSWITHINTEMPLATESOFDATA BOUNDCONTROLSARETREATED like dynamically added controls. Their events are not initially synchronized with the other controls ONTHEPAGE4HELIFETIMEOFSUCHCONTROLSBEGINSWITHTHEIRINSTANTIATIONTHEYRAISETHELIFECYCLE events one after the other until the control has caught up to the event during which it was added to the Controls collection. 5SUALLYTHISHASNOIMPLICATIONSFORDEVELOPERS5NLESSYOUHAVENESTEDDATA BOUNDCONTROLS YOUDONTNEEDTOBECONCERNEDABOUTTHIS&ORNESTEDDATA BOUNDCONTROLS THISBEHAVIORISABIT different. If a child control has been data bound, but its container control has not yet been bound, the data in the child control and the data in its container control can be out of sync. Imagine that you have a GridView control and that each row contains a bound @nkl@ksjHeop control. Furthermore, assume that the @nkl@ksjHeop’s data properties, such as @]p]Okqn_aE@, are set declaratively. The @nkl@ksjHeop will now bind to its datasource when the @]p]>ej`ejc event of the containing Cne`ReasROWOCCURS(OWEVER THECne`Reas might not yet have raised its Nks@]p]>kqj` event. In that case the @nkl@ksjHeop and containing control are out of sync. To avoid this you simply PUTTHEDATASOURCECONTROLˆTHEONEYOUHAVESETINTHE@]p]Okqn_aE@PROPERTYˆWITHINTHESAME template. Additionally, remove the declarative assignment and set it programmatically during the Nks@]p]>kqj` event. In this event the container’s data are bound and both controls can stay in sync. 3EE,ISTING FORASIMPLIFIEDSCENARIOTHATFULLYSUPPORTSANESTEDDATA BOUNDCONTROLWITHIN a template.

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Listing 1-7. Binding Nested Controls Within a Container’s Template 8dpihtihjo9dppl6++sss*s/*knc+-555+tdpih: 8da]`nqj]p9oanran: 8pepha:8+pepha: 8+da]`: 8^k`u: 8bknie`9bkni-nqj]p9oanran: 8`er: 8]ol6Cne`ReasE@9Cne`Reas-nqj]p9oanran=qpkCajan]pa?khqijo9B]hoa @]p]Okqn_aE@9Tih@]p]Okqn_a-kj`]p]^ej`ejc9Cne`Reas-[@]p]>ej`ejc kj`]p]^kqj`9Cne`Reas-[@]p]>kqj`kjejep9Cne`Reas-[Ejep kjhk]`9Cne`Reas-[Hk]`kjlnanaj`an9Cne`Reas-[LnaNaj`an kjnks`]p]^kqj`9Cne`Reas-[Nks@]p]>kqj`: 8?khqijo: 8]ol6Pailh]paBeah`Da]`anPatp9Ata_qpekjOui^kh OknpAtlnaooekj9Ata_qpekjOui^kh: 8EpaiPailh]pa: 8]ol6@nkl@ksjHeopnqj]p9oanrane`9``?kii]j` @]p]Okqn_aE@9K^fa_p@]p]Okqn_a- Oaha_pa`R]hqa9#8!>ej`$@ab]qhp%!:#: 8+]ol6@nkl@ksjHeop: 8]ol6K^fa_p@]p]Okqn_aE@9K^fa_p@]p]Okqn_a-nqj]p9oanran Oaha_pIapdk`9CapR]hqao PulaJ]ia9@]p]:8+]ol6K^fa_p@]p]Okqn_a: 8]ol6H]^ahE@9H]^ah-nqj]p9oanran Patp9#8!Ar]h$Ata_qpekjOui^kh%!:#:8+]ol6H]^ah: 8+EpaiPailh]pa: 8+]ol6Pailh]paBeah`: 8]ol6>kqj`Beah`@]p]Beah`9J]iaDa]`anPatp9J]ia OknpAtlnaooekj9J]ia+: 8+?khqijo: 8Ailpu@]p]Pailh]pa: Ailpu 8+Ailpu@]p]Pailh]pa: 8+]ol6Cne`Reas: 8+`er: 8]ol6Tih@]p]Okqn_aE@9Tih@]p]Okqn_a-nqj]p9oanran @]p]Beha9z+=ll[@]p]+@]p]*tih:8+]ol6Tih@]p]Okqn_a: 8+bkni: 8+^k`u: 8+dpih: -OVINGTHENESTEDDATASOURCEˆTHEK^fa_p@]p]Okqn_aINTHEEXAMPLEˆWITHINTHETEMPLATE assures that the events fires in the expected order.

Data Binding Events for Data-Bound Controls To help you understand the relationship between the page life cycle and data binding events, 4ABLE LISTSDATA RELATEDEVENTSINDATA BOUNDCONTROLS2EMEMBERTHATNOTALLCONTROLSSUP PORTALLEVENTSSHOWNINTHETABLE3OMEDATA BOUNDCONTROLSDONOTHAVEROWS FORINSTANCE WHICH means that a RowDataBound event cannot occur.

NNote

In the description of data-bound control’s behavior, I often refer to the term “containing control.” If there is no containing control, this assumes that the page is the container.

C H A P T E R 1 N U N D E R S T A N D I N G A S P . N E T

Table 1-2. Relationship Between Life Cycle Events and Data-Bound Events

Event

Typical Behavior

DataBinding

Raised before LnaNaj`an of containing control. Open database connections This is the beginning of binding procedure. here, if required.

Usage Hints

RowCreated

Raised after each row gets bound.

Manipulate content that does not depend on data binding.

ItemCreated

Raised after each item gets bound.

Manipulate content that does not depend on data binding.

RowDataBound

Bound data is now available for the row.

Format data, get and filter child rows or related data.

ItemDataBound

Bound data is now available for the item.

Format data, pull and filter child rows or related data.

DataBound

Marks the end of binding operation. All rows are bound now.

Do any action that requires all data available.

Login Control Events The login controls, which handle login and authentication, are highly sophisticated and powerful. 4HEYSUPPORTˆLIKETHEDATA BOUNDCONTROLSEVENTSˆSOMESPECIALEVENTSRELATEDTOTHEIRINTERNAL behavior. In most scenarios, the controls work well out of the box or just need some configuration using the web.configFILE(OWEVER IFYOUNEEDTOCHANGEORCUSTOMIZETHEBEHAVIOROREXTENDTHE AVAILABLEFEATURES YOULLNEEDTOKNOWTHEEVENTSFIREDDURINGTHEIRLIFECYCLESEE4ABLE  4HESE events are additional to the regular events raised by all controls, as previously explained in the sec tion “Dynamic Control Events.” Table 1-3. Relationship Between Life Cycle Events and Logging-In Events

Event

Typical Behavior

Usage Hints

LoggingIn

Raised during postback after LoadComplete.

Tasks required before the login procedure, such as opening a database connec tion, if required.

Authenticate

Raised next after LoggingIn.

Customize the authentica tion behavior itself.

LoggedIn

Raised after authentication.

Action required after success ful authentication, such as redirect to another page.

LoginError

Raised after failed authentication.

Do any action to handle failed authentication, such as displaying instructions.

View State The ASP.NET view state is a mechanism to track changes of the state of pages from one postback to the next. Postback occurs whenever a page sends the contents of a form back to the server. The NAMECOMESFROMTHEUNDERLYING(440COMMAND0/34THATISUSEDHEREANDTHEWAYTHATITTAKES the contents back to the server. View state is turned on by default and most developers don’t care

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about it. It contains the values of properties of ASP.NET controls changed since the last page cycle ANDISSTOREDINASERIALIZEDANDENCRYPTEDFORMATWITHINTHEPAGE ASSHOWNIN&IGURE %ACH postback sends all the information stored in it back to the server. As you may know, using view state in the default manner can lead to huge pages that consume a lot of bandwidth. It’s not easy to understand view state completely, and simply disabling it leads to controls not working or having fewer features. The real internal behavior is confusing and hard to understand. As long as you deal with simple applications, a basic idea might be enough. But when it comes to your own controls, complex pages, ORUSING!*!8 AGOODUNDERSTANDINGISAPREREQUISITE

Why Understanding View State Is Important Misunderstanding view state leads to leaking of sensitive data, being exploited by view state attacks, poor page performance, poor scalability, and headaches. Whatever you want to achieve with your APPLICATION &IGURE SHOWSTHESOURCEOFAPAGEWHICHYOUNEVERWANTTOSEE

Figure 1-11. The view state’s form field could grow. Simply disabling view state will not help, however, because you will probably lose some fea TURESTHATYOUNEEDANDLIKE%SPECIALLYCOMPLEXDATA BOUNDCONTROLSHOLDTHEIRSTATESFORPAGINGOR SORTINGINTHEVIEWSTATE)NFACT NOTHINGISWRONGWITHVIEWSTATEITSJUSTTHEWRONGORINAPPROPRI ate usage of it that causes problems. Now let’s move on by starting back at the beginning.

What View State Is Supposed to Do and Not Do

s 3TORESVALUESOFCONTROLSPROPERTIESBYKEYS SIMILARTOAHASHTABLE



s 4RACKSCHANGESTOINITIALVALUES



s 3ERIALIZESANDDESERIALIZESASAVEDDICTIONARYINAHIDDENFORMFIELD



s 2ESTORESSTOREDVALUESINTOCONTROLSPROPERTIES

C H A P T E R 1 N U N D E R S T A N D I N G A S P . N E T

These features are well known. Much more important is what the view state does not do:

s 2ETAINTHESTATEOFCLASSMEMBERSWITHOUTADDITIONALCODE



s 2EMEMBERSTATEINFORMATIONACROSSPAGELOADSPAGERELOADSBY'%4REQUEST



s !VOIDTHENEEDTOREPOPULATEDATAONEVERYREQUEST



s (OLDDATAINCONTROLSTHATAREPOSTEDBACKˆTHESO CALLEDSTICKYFORMBEHAVIOR

The last bullet point is probably the most confusing here. Many developers think that this is the only task that the view state has to do. Although the view state is involved in the process of holding the control’s visible data, it is not the originator of the process. That would be the initializing phase that retrieves the form’s data to set the control’s state, often described as “retaining the control state” or short, “control state.” View state is held in a hidden field with the name [[REASOP=PAh(IDDENvMEANSTHATTHE browser does not render the field, but the field itself and its content are visible in the page’s source. )TNEEDSTHEBANDWIDTHTWICEˆTHEFIRSTTIMEWHENTHEPAGEISSENTTOTHEBROWSERANDTHESECOND time when the browser sends the page back (that is, when a postback happens). A postback occurs VERYFREQUENTLYWHENAUSERNAVIGATESWITHINTHEAPPLICATIONANDUNLESSYOUUSEHYPERLINKSALMOST all actions are based on a form being sent back.

A Word Regarding Control State When talking about view state quite often the discussion includes the control state. The control state holds privately used control properties, especially for custom and complex controls in another serializable collection. Those data are stored within the view state storage that means by default the control state is part of the view state’s hidden field. Disabling the view state disables the control STATE TOO(OWEVER THEREISNODECLARATIVEWAYTOCONTROLTHECONTROLSTATESEPARATELY)NTHISDISCUS sion, the control state is just a matter of fact and you shouldn’t be worried about just another state of controls. Because it is essential for some controls, it is also not that critical because of the mini mal amount of dataWELL DEVELOPEDCONTROLSMIGHT hold there.

The Page Cycle from the View State Perspective The page cycle is very important to understanding view state completely, as several levels of the cycle treat view state explicitly. You can refer to the previous section to get an idea of the page cycle in a nutshell. In this section, I will repeat the major steps that actually handle view state. Each time the server receives a request for an .aspx page it will be processed by the ASP.NET engine through a specific number of steps. These include checking access security and restoring the session state. The session state holds data related to the current session, like session variables or logon information. At the end of the process the engine creates a class that consists of the markup CONVERTEDINTOCODEANDCODE BEHIND4HISSTEPGENERATESANINSTANCEOFTHATCLASS WHICHYIELDSTHE content of the Lnk_aooNamqaop method of the page’s handler. The page life cycle begins with the call to this method. Next, the initialization of the controls of the page occurs, followed by the life cycle phases of those controls. This includes the processing of the VIEWSTATE HANDLINGOFPOSTBACKDATAANDRELATEDEVENTSANDFINALLYTHEPROCESSINGOF(4-,CONTENT 4HELIFECYCLEOFTHEPAGEENDSWHENTHE(4-,ISCOMPLETELYRENDEREDANDHANDEDOVERTOTHE Web Server. The Web Server is responsible for sending the data over the wire to the browser. While the Web Server is sending the data, the garbage collector is already freeing up the released memory. 4HISISTRUEFORALLREQUESTSWITHOUTANYINTERACTIONORCUSTOMCODEREQUIRED(OWEVER WITHINTHIS cycle, view state has an extraordinary function and it makes your life as a control developer easier if you understand life cycles and their relation to view state.

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Step One—Instantiation The instantiation is the beginning of the life cycle of the page. The class built from markup and code, which represents the page, is instantiated and launched. But what actually happens and WHEREDOESTHEPAGESCODEGETSTORED!30.%4PAGESCONSISTOF(4-,MARKUPWITHCONTROLSAND code. First, the ASP.NET engine converts the text portion of the page and all markup into web con TROLS4HATMEANSTHEPAGEISNOWCOMPLETELYMADEOFCODE-OSTPARTSTHATCONSISTOF(4-,ARE replaced by Hepan]h?kjpnkh controls. Literals contain text that doesn’t need any further processing. This is required in order to avoid the extensive recognition process from ASP.NET engine. The ASP. .%4ENGINEISABLETORECOGNIZECHANGESMADETOEITHERMARKUPORCODEANDRE RUNSTHEPROCESS IF required. The features provided for a page are inherited from the L]ca class (Ouopai*Sa^*QE*L]ca). If code behind is being used, one more step is required. Using the l]npe]h keyword this class is MARRIEDWITHTHECODE BEHINDCLASSTHATISASSOCIATEDWITHTHE!308 page.

Building the Hierarchy of Controls The page is the top level of the hierarchy of controls. Because the L]ca class itself inherits from ?kjpnkh, it’s a control, too. Each control has exactly one parent and none, one, or many children. The elements placed declaratively in the page are children of the highest level. There is no limit to nesting levels for the control hierarchy. This leads to vast trees made of complex controls. One important control is DpihBkni (full name is Ouopai*Sa^*QE*Dpih?kjpnkho*DpihBkni). It cre ates the 8bkni: tag and determines the content sent during postback. The view state information is NECESSARILYPLACEDHERE9OUCANSEETHISINTHESAMPLESHOWNIN,ISTING  Listing 1-8. Simple ASPX Page with Controls 8dpihtihjo9dppl6++sss*s/*knc+-555+tdpih: 8da]`nqj]p9oanran: 8pepha:8+pepha: 8+da]`: 8^k`u: 8d-: =lnaoo)ReasOp]pa8+d-: 8bknie`9bkni-nqj]p9oanran: 8`er: 8]ol6Patp>ktnqj]p9oanranE@9ptpJ]ia+: 8^n+: =naukq_]hha`] 8]ol6@nkl@ksjHeopnqj]p9oanranE@9``hSd]p: 8]ol6HeopEpaiR]hqa9COaha_pa`9Pnqa:Caag8+]ol6HeopEpai: 8]ol6HeopEpaiR]hqa9J:Jan`8+]ol6HeopEpai: 8]ol6HeopEpaiR]hqa9S:@kj#pgjks8+]ol6HeopEpai: 8+]ol6@nkl@ksjHeop: 8^n+: 8]ol6>qppkjnqj]p9oanranE@9^pjOaj`Patp9Oaj`+: 8+`er: 8+bkni: 8+^k`u: 8+dpih: &IGURE SHOWSHOWITWILLLOOKLIKEINTHE6ISUAL3TUDIODESIGNER

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Figure 1-12. Simple page in Visual Studio Designer 4HE!30.%4ENGINEGENERATESTHEOUTPUTCODE AFRAGMENTOFWHICHISSHOWNIN,ISTING  Listing 1-9. Simple ASPX Page from Last Listing Compiled into Code in Debug Mode lq^he__h]oo`ab]qhp[]olt6[@ab]qhp(ENamqenaoOaooekjOp]pa(EDpplD]j`han w lner]paop]pe_k^fa_p[[beha@alaj`aj_eao7 lner]paop]pe_^kkh[[ejepe]heva`7 W@a^qccanJkjQoan?k`aY lq^he_`ab]qhp[]olt$% w ^]oa*=llNah]peraRenpq]hL]pd9z+@ab]qhp*]olt7 eb$[[ejepe]heva`% w opnejcWYrenpq]hBeha@alaj`aj_eao9jasopnejcWYwz+@ab]qhp*]olty7 [[beha@alaj`aj_eao9± ^]oa*CapSn]lla`Beha@alaj`aj_eao$renpq]hBeha@alaj`aj_eao%7 [[ejepe]heva`9pnqa7 y y W@a^qccanJkjQoan?k`aY lner]paDpihPepha[[>qeh`?kjpnkh[[_kjpnkh.$% w napqnjjasDpihPepha$%7 y W@a^qccanJkjQoan?k`aY lner]parke`[[>qeh`?kjpnkh[[_kjpnkh/$HeopEpai?khha_pekj[[_pnh% w HeopEpaiepai9pdeo*[[>qeh`?kjpnkh[[_kjpnkh0$%7 [[_pnh*=``$epai%7 HeopEpaiepai.9pdeo*[[>qeh`?kjpnkh[[_kjpnkh1$%7 [[_pnh*=``$epai.%7 HeopEpaiepai/9pdeo*[[>qeh`?kjpnkh[[_kjpnkh2$%7 [[_pnh*=``$epai/%7 y W@a^qccanJkjQoan?k`aY lner]paHeopEpai[[>qeh`?kjpnkh[[_kjpnkh0$% w HeopEpaiepai9jasHeopEpai$%7 epai*R]hqa9C7 epai*Oaha_pa`9pnqa7 epai*Patp9Caag7

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napqnjepai7 y W@a^qccanJkjQoan?k`aY lner]paHeopEpai[[>qeh`?kjpnkh[[_kjpnkh1$% w HeopEpaiepai9jasHeopEpai$%7 epai*R]hqa9J7 epai*Patp9Jan`7 napqnjepai7 y W@a^qccanJkjQoan?k`aY lner]paHeopEpai[[>qeh`?kjpnkh[[_kjpnkh2$% w HeopEpaiepai9jasHeopEpai$%7 epai*R]hqa9S7 epai*Patp9@kj#pgjks7 napqnjepai7 y W@a^qccanJkjQoan?k`aY lner]pa>qppkj[[>qeh`?kjpnkh^pjOaj`$% w >qppkj^qppkj9jas>qppkj$%7 ^]oa*^pjOaj`9^qppkj7 ^qppkj*=llhuOpuhaOdaapOgej$pdeo%7 ^qppkj*E@9^pjOaj`7 ^qppkj*Patp9Oaj`7 napqnj^qppkj7 y W@a^qccanJkjQoan?k`aY lner]pa@nkl@ksjHeop[[>qeh`?kjpnkh``hSd]p$% w @nkl@ksjHeopheop9jas@nkl@ksjHeop$%7 ^]oa*``hSd]p9heop7 heop*=llhuOpuhaOdaapOgej$pdeo%7 heop*E@9``hSd]p7 pdeo*[[>qeh`?kjpnkh[[_kjpnkh/$heop*Epaio%7 napqnjheop7 y W@a^qccanJkjQoan?k`aY lner]paDpihBkni[[>qeh`?kjpnkhbkni-$% w DpihBknibkni9jasDpihBkni$%7 ^]oa*bkni-9bkni7 bkni*E@9bkni-7 EL]noan=__aookn]__aookn9bkni7 ]__aookn*=``L]noa`Oq^K^fa_p$± jasHepan]h?kjpnkh$XnXj8`er:XnXj%%7 Patp>kt^kt9pdeo*[[>qeh`?kjpnkhptpJ]ia$%7 ]__aookn*=``L]noa`Oq^K^fa_p$^kt%7 ]__aookn*=``L]noa`Oq^K^fa_p$± jasHepan]h?kjpnkh$XnXj8^n+:XnXj± =naukq_]hha`]XnXj%%7

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@nkl@ksjHeopheop9pdeo*[[>qeh`?kjpnkh``hSd]p$%7 ]__aookn*=``L]noa`Oq^K^fa_p$heop%7 ]__aookn*=``L]noa`Oq^K^fa_p$± jasHepan]h?kjpnkh$XnXj8^n+:XnXj%%7 >qppkj^qppkj9pdeo*[[>qeh`?kjpnkh^pjOaj`$%7 ]__aookn*=``L]noa`Oq^K^fa_p$^qppkj%7 ]__aookn*=``L]noa`Oq^K^fa_p$± jasHepan]h?kjpnkh$XnXj8+`er:XnXj%%7 napqnjbkni7 y W@a^qccanJkjQoan?k`aY lner]paDpihDa]`[[>qeh`?kjpnkhDa]`-$% w DpihDa]`da]`9jasDpihDa]`$da]`%7 ^]oa*Da]`-9da]`7 da]`*E@9Da]`-7 DpihPephapepha9pdeo*[[>qeh`?kjpnkh[[_kjpnkh.$%7 EL]noan=__aookn]__aookn9da]`7 ]__aookn*=``L]noa`Oq^K^fa_p$pepha%7 napqnjda]`7 y W@a^qccanJkjQoan?k`aY lner]parke`[[>qeh`?kjpnkhPnaa$`ab]qhp[]olt[[_pnh% w pdeo*Ejepe]heva?qhpqna$%7 EL]noan=__aookn]__aookn9[[_pnh7 ]__aookn*=``L]noa`Oq^K^fa_p$± jasHepan]h?kjpnkh$XnXjXnXj8@K?PULAdpihLQ>HE?X)++S/?++@P@TDPIH-*,± Pn]joepekj]h++AJXXdppl6++sss*s/*knc+PN+tdpih-+@P@+tdpih-)± pn]joepekj]h*`p`X:XnXjXnXj8dpihtihjo9Xdppl6++sss*s/*knc+-555+tdpihX:XnXj%%7 DpihDa]`da]`9pdeo*[[>qeh`?kjpnkhDa]`-$%7 ]__aookn*=``L]noa`Oq^K^fa_p$da]`%7 ]__aookn*=``L]noa`Oq^K^fa_p$jasHepan]h?kjpnkh$XnXj8^k`u:XnXj± 8d-:XnXj=lnaoo)ReasOp]pa8+d-:XnXj%%7 DpihBknibkni9pdeo*[[>qeh`?kjpnkhbkni-$%7 ]__aookn*=``L]noa`Oq^K^fa_p$bkni%7 ]__aookn*=``L]noa`Oq^K^fa_p$± jasHepan]h?kjpnkh$XnXj8+^k`u:XnXj8+dpih:XnXj%%7 y W@a^qccanJkjQoan?k`aY lner]paPatp>kt[[>qeh`?kjpnkhptpJ]ia$% w Patp>kt^kt9jasPatp>kt$%7 ^]oa*ptpJ]ia9^kt7 ^kt*=llhuOpuhaOdaapOgej$pdeo%7 ^kt*E@9ptpJ]ia7 napqnj^kt7 y W@a^qccanJkjQoan?k`aY lnkpa_pa`kranne`arke`Bn]iaskngEjepe]heva$% w ^]oa*Bn]iaskngEjepe]heva$%7 pdeo*[[>qeh`?kjpnkhPnaa$pdeo%7

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^]oa*=``Sn]lla`Beha@alaj`aj_eao$[[beha@alaj`aj_eao%7 ^]oa*Namqaop*R]he`]paEjlqp$%7 y W@a^qccanJkjQoan?k`aY lq^he_kranne`aejpCapPulaD]od?k`a$% w napqnj)-234/4305-7 y W@a^qccanJkjQoan?k`aY lq^he_kranne`arke`Lnk_aooNamqaop$Dppl?kjpatp_kjpatp% w ^]oa*Lnk_aooNamqaop$_kjpatp%7 y ++Lnklanpeao lnkpa_pa`Dppl=llhe_]pekj=llhe_]pekjEjop]j_a w cap w napqnjpdeo*?kjpatp*=llhe_]pekjEjop]j_a7 y y lnkpa_pa`@ab]qhpLnkbehaLnkbeha w cap w napqnj$@ab]qhpLnkbeha%pdeo*?kjpatp*Lnkbeha7 y y y The code is not very readable, but this is what generated code is supposed to look like, right? There is no need to do anything special with it, but rather to learn what is going on internally. Note two things here. First, the declarative assignment of attributes is being replaced with simple prop erty assignments. See the following markup: 8]ol6>qppkjpatp9Oaj`: It becomes this in the generated class: ^qppkj-*Patp9Oaj` Second, all literal stuff is placed in strings and copied into the final page “as is,” which is shown in the following snippet: jasHepan]h?kjpnkh$XnXj8+^k`u:XnXj8+dpih:XnXj%% Once the class is complete, the engine proceeds to the next step.

C H A P T E R 1 N U N D E R S T A N D I N G A S P . N E T

Step Two—Initializing After creating the control hierarchy, all the controls of the page are moved into the initialization state. This becomes apparent by raising the Ejep event. In this phase not only are the controls ready, but they also have their static, declarative properties assigned.

NNote

“Declarative” is everything that’s written within the markup and not in code fragments.

Whether or not a property has been declaratively assigned, you still can change the value any time BEFORETHERENDERPROCESSISCOMPLETE(OWEVER BECAUSE)MTALKINGABOUTVIEWSTATE THEINITIALIZA tion step plays a special role regarding property values.

View State Tracks Changes View state tracks changes of properties. This is a special function of the Op]pa>]c class defined in the Ouopai*Sa^*QE namespace, which holds the data behind the scenes. Tracking starts during the Initializing step of the page. In order to recognize the default value and the changed one, the Op]pa>]c compares the initialized value set by declarative markup with the current value set any time later programmatically. Even if the results look the same, the view state treats the data in a different way.

View State and Dynamic Controls Using dynamic controls, you’ll know that technically it’s possible to add controls any time before the page render process is complete. The view state is not that flexible. Adding controls using ?kjpnkho*=`` method must take place in the initializing phase. Otherwise, the Op]pa>]c class does not recognize the Ejep event at the right time and does not start tracking changes. You still can add controls anytime, but for those controls the view state will not work. You might find problems here OCCASIONALLY ASTHEMAJORITYOFCONTROLSBEINGADDEDDYNAMICALLYˆSUCHASTHEH]^ahCONTROLˆDONT require property value tracking. The golden rule states that in order to “take care of the view state, whether it’s required or not, add dynamic controls during the Initializing step.”

Step Three—Loading the View State View state data is saved into a hidden field called [[REASOP=PA. It’s transmitted back to the server only during a POST operation, which forces a postback.

NNote

You can completely ignore page requests that use GET for this step. Such requests do not interact with view state at all.

In this step the engine decodes values from the hidden field and assigns them to the controls, looping recursively through the control hierarchy. Also in this phase the validity of the view state is checked. There are several reasons why the view state could become invalid. One reason is that the control hierarchy has been changed during postback and the control is not at the expected place, or removed completely.

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)FEVERYTHINGISFINE THEENGINEPROCEEDSTOTHENEXTSTEP3EETHESECTIONh6IEW3TATE!NTI Patterns” for an example of what’s going on when it went wrong.

Step Four—Loading Postback Data After loading and restoring the view state, the form data is processed. Not all controls can return data. To let the engine know whether it has to look for data sent back, the ELkop>]_g@]p]D]j`han interface is recognized. Each control implementing this interface might send form data back. Form DATAISSENTBACKINTHE(440PROTOCOLASIDnVALUEPAIRS Iu_heajpe`9r]hqa The page class looks for a control with a ?heajpE@ that equals “Myclientid”. When found, it checks whether the control implements the ELkop>]_g@]p]D]j`han interface. If it does this, the page CLASSCALLSTHEONLYMETHODDEFINEDTHEREˆHk]`Lkop@]p]. That means that the control itself manages the loading of data, which opens up a great way of changing behavior and adding custom code. Concerning view state, this behavior is very significant. The ability to get the values of controls back between postbacks is called “sticky form” behavior. It’s one of the best features of ASP.NET. Let me explain this in more detail using the example of a Patp>kt control. The Patp>kt has a property Patp. It also implements the ELkop>]_g@]p]D]j`han interface. Once a page with the textbox control is posted back, the Hk]`Lkop@]p] method reads the value of the control out of the view state and writes it into the PatpPROPERTY4HEDEFAULTVALUEˆTHATWASPROBABLYSETDECLARATIVELYˆISOVERWRITTEN9OU can easily check this with the following definition: 8]ol6Patp>ktnqj]p9oanranE@9ptpJ]iaPatp9+: 4HERENDERPROCESSTRANSFORMSTHISMARKUPINTO(4-,FORM 8ejlqppula9patpe`9ptpJ]iaj]ia9ptpJ]ia+: If the user now enters some text here, like “It’s a geek”, the form transmitted back to the server contains at least this line: ptpJ]ia9Ep#o]caag This data pair becomes part of the Namqaop*Bkni collection. The key is “txtName” and the value is “It’s a geek”. The page class hands this data pair to the Hk]`Lkop@]p] method. Internally there is nothing surprising here. Using Reflector, you can look into the relevant code inside Ouopai*Sa^*`hh SEE,ISTING   Listing 1-10. Disassembled Code of the LoadPostData Method lnkpa_pa`renpq]h^kkhHk]`Lkop@]p]$opnejclkop@]p]Gau(± J]iaR]hqa?khha_pekjlkop?khha_pekj% w ^]oa*R]he`]paArajp$lkop@]p]Gau%7 opnejcpatp9pdeo*Patp7 opnejcopn.9lkop?khha_pekjWlkop@]p]GauY7 eb$pdeo*Na]`Kjhu""patp*Amq]ho$opn.(Opnejc?kil]neokj*Kn`ej]h%% w pdeo*Patp9opn.7 napqnjpnqa7 y napqnjb]hoa7 y

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This code snippet is from Patp>kt, and the one and only property filled by a postback is Patp. 4HECONTROLMIGHTHAVEBEENSETREAD ONLYANDTHEREFORETHISISCHECKEDFIRSTpdeo*Na]`Kjhu). Also, as the code compares the old value and the new one, it’s written only if the value has been changed. Why is this additional check required? You might assume that comparing takes more time than ASSIGNINGAPROPERTYˆEVENIFTHEREISNOTHINGTORENDERATTHISSTAGE7ELL THEREASONISVIEWSTATE To understand this, take a look into the code for the PatpPROPERTYIN,ISTING  Listing 1-11. Disassembled Code of Text Method of the TextBox Class lq^he_renpq]hopnejcPatp w cap w opnejcopn9$opnejc%pdeo*ReasOp]paWPatpY7 eb$opn9jqhh% w napqnjopn7 y napqnjopnejc*Ailpu7 y oap w pdeo*ReasOp]paWPatpY9r]hqa7 y y The value is not stored in a private field, but only in view state. The tracking feature of the underlying Op]pa>]c class handles changes as well. If nothing has changed, it’s not recommended to assign the value to view state, or the Op]pa>]c class will start tracking. If there is nothing to track, it doesn’t make sense to do so, and the Hk]`Lkop@]p] method is clever enough to know. One major aspect many developers overlook is the role of view state in the handling of postback data. The form data loading procedures do not involve view state. More than that, they try to avoid any interaction with view state. The form data handling and stickiness behavior has nothing to do with the view state. The stickiness is a feature that comes with the ELkop>]_g@]p]D]j`han interface. *USTFORCLARITY ,ISTING SHOWSITINITSENTIREGLORY Listing 1-12. Code of IPostBackDataHandler Interface lq^he_ejpanb]_aELkop>]_g@]p]D]j`han w ^kkhHk]`Lkop@]p]$opnejclkop@]p]Gau(± J]iaR]hqa?khha_pekjlkop?khha_pekj%7 rke`N]eoaLkop@]p]?d]jca`Arajp$%7 y You know now that view state tracks changes and stores these changes. You know, too, that the stickiness of the form has nothing to do with view state. The Hk]`Lkop@]p] method just explores the values sent back to server and restores it into the appropriate properties. .OW ALLTHECONTROLSHAVEBEENINITIALIZED PROPERLYFILLEDWITHDECLARATIVEDATA OVER WRITTEN with data posted back from the browser, and are ready to enter the next state.

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Step Five—Loading Step Most descriptions of ASP.NET put user code into the Hk]` event. In the explanation of life cycles, you read about this important step because it signals to us that the control is now “ready.” Even if you don’t want to do anything else with the control, it’s ready to be rendered. This is why the best step for adding custom code and modifying the behavior of the page is the load step. Internally, it’s much easier, because there is nothing to do within the control. Anything that is supposed to happen here is up to you.

Step Six—Raising Postback Events Several controls can fire events, depending on the form data posted back. After the loading step, the events are fired one by one. For example, the >qppkj control can fire a ?he_g event, whereas the @nkl@ksjHeop fires Oaha_pa`Ej`at?d]jca`. This is another major feature that makes the dynamic portion of an ASP.NET page so powerful and easy to program. There are two kinds of events fired during the page’s postback. One kind is responsible for changes, indicated by the suffix [?d]jca. The implementation of ELkop>]_g@]p]D]j`han is responsible for recognizing this and firing the appropriate event by calling the N]eoaLkop@]p]?d]jca`Arajp method. In the case of the Patp>kt example, the event exposed by the class is KjPatp?d]jca`. The other kind of event is the trigger event. For example, in the case of a >qppkj this is a ?he_g EVENT4HEREISNOSPECIALSTATEREQUIREDANDNODATATOCOMPARE!SYOUCANSEEIN,ISTING  TO handle trigger events the ELkop>]_gArajpD]j`han interface is used. Listing 1-13. Code of IPostBackEventHandler Interface lq^he_ejpanb]_aELkop>]_gArajpD]j`han w rke`N]eoaLkop>]_gArajp$opnejcarajp=ncqiajp%7 y To understand what happens internally, we’ll look into the N]eoaLkop>]_gArajp method. ,ISTING ISFORA>qppkj control. Listing 1-14. Code of Typical Implementation of IPostBackEventHandler Interface lnkpa_pa`renpq]hrke`N]eoaLkop>]_gArajp$opnejcarajp=ncqiajp% w ^]oa*R]he`]paArajp$pdeo*QjemqaE@(arajp=ncqiajp%7 eb$pdeo*?]qoaoR]he`]pekj% w pdeo*L]ca*R]he`]pa$pdeo*R]he`]pekjCnkql%7 y pdeo*Kj?he_g$Arajp=nco*Ailpu%7 pdeo*Kj?kii]j`$jas?kii]j`Arajp=nco$ pdeo*?kii]j`J]ia(pdeo*?kii]j`=ncqiajp%%7 y !SYOUCANSEE THISMETHODRAISESMORETHANONEEVENTINAPREDEFINEDANDHARD CODEDORDER 3EVERALOTHERACTIONSTAKEPLACEFIRSTˆSUCHASVALIDATIONˆBUTTHEEVENTSBEINGFIREDAREUNCONDI tional. Again, all of these events can only happen during a postback. Calling the page using GET will do nothing. If you have a @nkl@ksjheop, and if you change the current index programmatically, nothing will happen unless the page is posted back. This is different from the windows programming model, where the controls can fire events immediately and independently of a particular state.

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Step Seven—Storing the View State After all events have been fired, the current state of each control’s property changes needs to be stored. The tracked changes are retrieved recursively through the controls hierarchy. To get the value back, the O]raReasOp]pa method of each control is called. The collection of data is then serial IZEDANDENCODEDUSING"ASE In the next step, the string is saved to the hidden field with id [[REASOP=PA.

Step Eight—Rendering the Page The render process runs through all the controls and allows them to render. This is done by a recursive call to all Naj`an?kjpnkh methods. The DpihBkni control mentioned at the beginning is responsible for creating the [[REASOP=PA hidden field, which is the container for view state data.

The True Role of View State The eight states of the life cycle are virtually all important for view state. There are several more steps the various life cycles could run through, but these steps don’t affect view state, so I’ll exclude them for now. To understand the view state, it’s crucial to know what the purpose of view state is. As the name implies, view state stores status information. But what kind of status is it? The hierarchy of controls and the default values of properties are defined in the declarative part of the page. Take a look at this markup: 8]ol6H]^ahnqj]p9oanranPatp9Saha]njreasop]paBkjp)>kh`9pnqa+: Neither the text “We learn viewstate” nor the value >kh` of the Bkjp property is stored in view state. The values are assigned during the initializing phase. View state, in contrast, tracks changes made programmatically. This leads to the first definition about view state.

NNote

View state becomes important only if the page contains custom code.

(OWEVER IFAPAGECONTAINSCUSTOMCODE THISDOESNOTNECESSARILYMEANTHATVIEWSTATEISREQUIRED ,ETSLOOKINTOANOTHERCODESNIPPET4HEFOLLOWINGEXAMPLEIN,ISTING HASTWOBUTTONS"OTHCAUSE a postback, but only one has an Kj?he_g event attached and handled to access properties in code. Listing 1-15. Markup of the View State Test 8]ol6H]^ahE@9H]^ahIaoo]canqj]p9oanranPatp9Saha]njreasop]pa:8+]ol6H]^ah: 8^n+: 8]ol6>qppkjE@9>qppkjOq^iepnqj]p9oanrankj_he_g9>qppkjOq^iep[?he_g Patp9?d]jcaPatpSe`pd9-1,lt+: 8^n+: 8]ol6>qppkjE@9>qppkjAilpunqj]p9oanranPatp9Jk?d]jca Se`pd9-1,lt+: !SSHOWNIN,ISTING  THECODEOFTHECLICKHANDLERISSIMPLE TOO Listing 1-16. Code of the Click Handler lnkpa_pa`rke`>qppkjOq^iep[?he_g$k^fa_poaj`an(Arajp=ncoa% w H]^ahIaoo]ca*Patp9DahhkCaag7 y

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!TTHEFIRSTCALLOFTHEPAGETHE!308MARKUPISPROCESSEDANDALLVALUESOFPROPERTIESARESET especially the text “We learn viewstate” for the H]^ah. View state stores nothing and therefore con tains only internal information without custom data: 8ejlqppula9de``ajj]ia9[[REASOP=PAe`9[[REASOP=PA± r]hqa9+sAL@sQHHPAtJfIvJ@EtJfNgVCj1]if>oKK]l2?rN^lQI1@5Ihck+: Now click on the button “No Change”. This forces the page to postback and reload, but nothing more happens, because no custom code is involved. Now click on the other button “Change Text”. Again a postback occurs, but now the handler processes the Kj?he_g event. In the code, the text of the label gets a new value. View state is changed to this: 8ejlqppula9de``ajj]ia9[[REASOP=PAe`9[[REASOP=PAr]hqa9+sAL@sQHHPAtJfIvJ@Et fMLV>U?=cILV>U?=cAL@tU?DcNQVTd,>MpEUSto^u>DVSRnESNgVDPaJ--HePr1>F,tO`au,H,Mojg4+: As you see, the coded part is bigger and obviously contains more information. This is no sur prise. If you click now on the other button “No Change”, the page loads as expected and no custom CODEISRUN(OWEVER THETEXTOFTHELABELISSTILLh(ELLOGEEK
v4HEREISNOCUSTOMCODEˆTHEINITIAL izing phase has obviously passed and has set the declaratively assigned values. But the change made PROGRAMMATICALLYINANEARLIERPOSTBACKISSTILLTHEREˆITSPERSISTENT That’s really the purpose of view state. During postbacks, it makes programmatic changes to control properties persistent. To check whether this behavior is really managed by view state, just disable it using the
View State Anti-Patterns Improper use of view state is easily avoided once you really understand how it works. To make things clear, I’ll explain the most frequent misuse scenarios. Examples of how not to use view state will help you understand how to use view state correctly:

s &ORCINGADEFAULT



s 0ERSISTINGSTATICDATA



s 0ERSISTINGhCHEAPvDATA



s )NITIALIZINGCHILDCONTROLS



s !DDINGCONTROLSDYNAMICALLY



s )NITIALIZINGDYNAMICALLYCREATEDCONTROLS I’ll explain each of these scenarios to make things as clear as possible.

C H A P T E R 1 N U N D E R S T A N D I N G A S P . N E T

Forcing a Default Forcing a default value is a very common misuse. Fortunately, it’s even easier to fix. It’s also a good demonstration of the KISS5 principle. The developers of ASP.NET did a tremendous job to give us APOWERFULANDWELL DESIGNEDTOOLKIT4HEWHOLEFRAMEWORKISANINFRASTRUCTURETHINGANDPROVIDES stable and reliable blocks of code for basic stuff. Doing too much infrastructure work is a signal that something is going wrong. Assume that you want to store some private data used in a user control. The following code in ,ISTING USESTHEVIEWSTATE WHICH INPRINCIPLE ISNOTABADIDEA Listing 1-17. DON’T TRY THIS AT HOME: a wrongly written user control lq^he__h]ooIu?kjpnkh6Sa^?kjpnkh w lq^he_opnejcIu@]p] w capwnapqnjReasOp]paWIu@]p]Y]oopnejc7y oapwReasOp]paWIu@]p]Y9r]hqa7y y lnkpa_pa`kranne`aKjHk]`$Arajp=ncoa% w eb$EoLkop>]_g% w pdeo*Iu@]p]9OaooekjW?kjpnkhIu@]p]Y]oopnejc7 y ^]oa*KjHk]`$%7 y y 9OUMAYHAVEWRITTENCODELIKETHISBEFORE)TSNOTABADSTYLEITSSIMPLYWRONG4OUNDER stand my harsh judgment, let’s examine the intent of the control. The developer wrote a user control with the public property MyData. This gives other developers access to it in order to put the control into a defined state using markup like this: 8]he]o6iu_kjpnkhnqj]p9oanranPatp9Odkspdeoh]^ahe`9iu?kjpnkh-+: 4HISCOMPILESANDRUNSWELLWITHOUTANYEXCEPTIONS(OWEVER ITDOESNTWORKASEXPECTED because the MyData property is never set. Instead, the view state of the page starts growing because THEVIEWSTATEFIELDSTORESTHISPRIVATEINFORMATION&ROMTHATPERSPECTIVE ITSDOINGWELLITHOLDS some data. Also, remember the life cycle events. It’s boring to repeat them again and again, but EVERYTHINGIN!30.%4ISBASEDONTHELIFECYCLE)N,ISTING THECODEISWRITTENINTOTHEKjHk]` method. But the Hk]` stage is too late. View state already tracks changes, and now it’s being over written. That’s why it doesn’t make sense to write the data there. Let’s improve our example (see ,ISTING   Listing 1-18. Save to Be Used at Home: A Well-Written Control lq^he__h]ooIu?kjpnkh6Sa^?kjpnkh w lq^he_opnejcIu@]p] w capw eb$ReasOp]paWIu@]p]Y99jqhh% 5. Keep it Simple, Stupid

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napqnjOaooekjW?kjpnkhIu@]p]Y]oopnejc7 ahoa napqnjReasOp]paWIu@]p]Y]oopnejc7 y oapwReasOp]paWIu@]p]Y9r]hqa7y y  y This involves less code and it’s working well. The default value in the session is now used without touching view state. Simply putting the control onto the page does not increase the size of view state. KjHk]` is out of the way here. The assignment of properties happens in the Initializing PHASEˆEARLYENOUGHTOSETVALUESPROPERLY)NCASETHEUSEROFTHECONTROLSETSTHE-Y$ATAPROPERTY programmatically, view state is in full cry and stores the changes silently in the hidden field.

Persisting Constant Data A lot of data used in a page’s code never changes during the life of the page or during the user’s ses sion. Assume your application has some “My” section that is customizable by the user. After the user is logged on, his or her name appears at the top of each page. Assume further that a user con trol is being written to achieve this. 8]ol6h]^ahe`9h^hQoannqj]p9oanran+: )NTHECODE BEHINDPORTIONTHENAMEISSET lq^he__h]ooIu?kjpnkh6Sa^?kjpnkh w lnkpa_pa`kranne`aKjHk]`$Arajp=ncoa% w h^hqoan*Patp9?qnnajpQoan*J]ia7 ^]oa*KjHk]`$%7 y y 4HISISCODETHATWOULDWORKWELL(OWEVER ITSDOINGSOMETHINGUNDERTHEHOODTHATYOU don’t want. The label has its own view state and, as a child control of the user control, it will store its changed properties in the parent’s view state. The user control is going to recognize this and store the change of view state. Storing the label’s text value in view state doesn’t make sense as, each time it’s loaded, the value is pulled from the ?qnnajpQoan class. The default behavior of controls is an implicit usage of view state. Either you assign it once, and hold data in view state, or you need to prevent it from using view state. The solution I would recommend looks very easy: 8]ol6h]^ahe`9h^hQoannqj]p9oanranAj]^haReasop]pa9b]hoa+: Disable view state on the control level and it will work like a charm. The next pattern extends this solution by presenting an alternative solution.

Persisting Cheap Data Sometimes you use data that changes frequently, depending on user action or external conditions. Assume you want to show a list of data on your page. It is a small list and it doesn’t change fre QUENTLY"UTITCOULDCHANGEORGROWATANYTIME9OURSITEISALREADYUSINGADATABASEITSFASTAND there is nothing wrong with pulling the data from a table.

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8]ol6`nkl`ksjheopnqj]p9oanrane`9``hIu@]p]@]p]PatpBeah`9J]ia± @]p]R]hqaBeah`9E@+: 4HEFICTITIOUS CODE BEHINDPORTIONCOULDLOOKLIKETHIS lq^he__h]ooIu?kjpnkh6Sa^?kjpnkh w lnkpa_pa`kranne`aKjHk]`$Arajp=ncoa% w eb$EoLkop>]_g% w ``hIu@]p]*@]p]Okqn_a9@=H*Mqanu@`h@]p]$%7 ``hIu@]p]*@]p]>ej`$%7 y ^]oa*KjHk]`$%7 y y 4HISIS AGAIN WORKINGWELLANDNOBODYWOULDSEEANYISSUESHERE(OWEVER THEREISSOMETHING here that is easily overlooked. Databound controls need to remember their state, for instance, to hold the last selected option of a dropdownlist after postback. I discussed this previously and called this smart behavior “stickiness.” You don’t want to lose the form’s sticky behavior. You might there fore assume that switching view state off is not a solution either. But stickiness is part of the control STATEITSMADEBYCHECKINGTHEFORMDATA)TSNOTRELATEDTOVIEWSTATE ASSOMEDEVELOPERSTHINK The reason you run into trouble with view state is that it grows each time the page reloads. This time the solution is not so simple. Switching off view state is only half of the answer: 8]ol6`nkl`ksjheopnqj]p9oanrane`9``hIu@]p]@]p]PatpBeah`9J]ia± @]p]R]hqaBeah`9E@Aj]^haReasOp]pa9b]hoa+: 4HECODE BEHINDISALMOSTTHESAME EXCEPTYOUPULLTHEDATAEVERYTIMETHECONTROLLOADSNOTE the missing eb statement): Lq^he__h]ooIu?kjpnkh6Sa^?kjpnkh w lnkpa_pa`kranne`aKjHk]`$Arajp=ncoa% w ``hIu@]p]*@]p]Okqn_a9@=H*Mqanu@`h@]p]$%7 ``hIu@]p]*@]p]>ej`$%7 ^]oa*KjHk]`$%7 y y Now view state is as clean as possible. But the sticky form behavior has gone, too. Trying this, you might think you’ve found a bug in this book and that the author is wrong about view state. The fault is not view state itself. It still has no function because the control state is restoring the DATAFROMPOSTBACKVALUES(OWEVER LETSOVERWRITETHISBECAUSETHEKjHk]` event is fired after all states are restored. This is, again, a life cycle issue. Understanding the life cycle leads us to the solu TION-OVETHELASTCODEFRAGMENTASISTOANOTHERSTEPINTHELIFECYCLEˆKjEjep: lq^he__h]ooIu?kjpnkh6Sa^?kjpnkh w lnkpa_pa`kranne`aKjEjep$Arajp=ncoa% w ``hIu@]p]*@]p]Okqn_a9@=H*Mqanu@`h@]p]$%7 ``hIu@]p]*@]p]>ej`$%7

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^]oa*KjEjep$%7 y y This solution is both clean and simple. KjEjep fires before the control state restores the values. It pulls static data from a fast database, puts it directly into the control, forces the render process before the control restores its state, and everything is fine. The render process is an important step here, made by calling the @]p]>ej` method.

NTip You’ll probably want to avoid heavy database access whenever possible. Instead, you’ll probably store small data portions in XML files and maintain changes there. I would recommend using a database anyway. Modern implementations, like Microsoft SQL Server™, hold frequently requested data in memory. The amount of data requested is small, and the connection is usually 1GB or 10GB Ethernet. A powerful data access layer will also cache the data locally, so that in reality nothing is transferred between the servers. The slowest part of the connection is from the Web Server to the user. He or she will have ISDN, DSL, or a mobile connection. Storing the small portion of data in view state sends the data three times over the wire: once when the user loads the page (as visible data in the dropdown control), once in view state, and the third time when the form is sent back (as view state is part of the form’s field collection). Calling a database frequently is not torture; this is the reason for a database.

Initializing Child Controls One paradigm you might hear frequently about ASP.NET is to do things declaratively. Whatever you can do directly within the !308PAGE DOIT
(OWEVER THISHASSOMEIMPLICATIONSANDLIMITATIONS and eventually you must start doing some work programmatically. The trouble is that initializing controls programmatically is not straightforward. As shown before, you can do this in KjHk]`, but this could cause the view state to grow and, in any case, it’s not necessary to use view state when merely setting defaults. Even KjEjep is not the best solution because view state will still track changes and catch the settings. If you need view state and can’t disable it, you’ll have to live with THISBEHAVIOR"ECAUSETHECONTROLSVIEWSTATETRACKSCHANGESFROMTHEBOTTOMUPˆSAY FROMTHE LASTLEAFCONTROLINTHECONTROLHIERARCHYUPTOTHETREESROOTˆTHEKjEjep for child controls is done when the current KjEjep is called. 8]ol6h]^ahe`9h^h@]panqj]p9oanran+: )NTHECODE BEHINDPORTION YOUSETTHETEXTBYASSIGNINGTHECURRENTDATE lq^he__h]ooIu?kjpnkh6Sa^?kjpnkh w lnkpa_pa`kranne`aKjEjep$Arajp=ncoa% w h^h@]pa*Patp9@]paPeia*Jks*PkHkjc@]pa$%7 ^]oa*KjEjep$%7 y y Even if this is the earliest event possible, it’s already too late. The label is initialized before the user control, and view state is already tracking changes. This means that the date persists in view STATE WHICHDOESNTMAKESENSEˆTHISISTHESAMESITUATIONFACEDINTHECURRENTUSERNAMEEXAMPLE Disabling view state has been discussed before, but this is not always a solution. Perhaps you have tried this: 8]ol6h]^ahe`9h^h@]pnqj]p9oanranPatp98!9@]paPeia*Jks*PkHkjc@]paOpnejc$%!:+:

C H A P T E R 1 N U N D E R S T A N D I N G A S P . N E T

This is not possible, because ASP.NET doesn’t allow the initializing of properties in that way. Using databinding syntax 8!!: is no solution, either. Let’s assume that for some reason you want to assign the value by code. And you want to use view state for some other reason as well. You may think about KjLnaEjep, but this event isn’t recursive and appears only on the page level. So, what’s going on here? It’s interesting that the KjEjep event behaves slightly different depending on how you get access to it. The obvious way is to override the event HANDLER4HISISEASY WELL SUPPORTEDIN)NTELLI3ENSE ANDTHEMOSTCOMMONSOLUTION9OUCANATTACH events declaratively, too. As I said before, this is one of the major paradigms of ASP.NET. 8]ol6h]^ahe`9h^h@]panqj]p9oanranKjEjep9h^h@]pa[Ejep+: 4HISHANDLERISFIREDBEFORETHEINTERNALINITIALIZATIONTAKESPLACEˆBEFORETHEPn]_gReasOp]pa method is called and the view state starts tracking changes. Referring to the control’s life cycle, there ISASUBTLEDIFFERENCEBETWEENTHEDECLARATIVELYATTACHEDEVENTANDOVERRIDINGTHEMETHOD*USTSET THETEXTINTHECODE BEHINDASYOUWOULDBEFORE lq^he__h]ooIu?kjpnkh6Sa^?kjpnkh w lq^he_rke`h^h@]pa[Ejep$k^fa_poaj`an(Arajp=ncoa% w h^h@]pa*Patp9@]paPeia*Jks*PkHkjc@]pa$%7 y y

NTip If you’re wondering whether to use declarative events or just wire up to code—remember the basic rule: “Whatever we can do easily and safely the declarative way is our primary programming technique.” !NOTHERSOLUTIONCOMESTOMINDIFYOUREANEXPERIENCEDDEVELOPEROFOBJECT ORIENTEDSOFTWARE Each object starts its life with the call of the object’s constructor. Usually the constructor is the place TOINITIALIZETHEOBJECT(OWEVER IN!30.%4THELIFEOFCONTROLSBEGINSSOMETIMELATER INTHEINI tialization phase. You may subclass the control and override the constructor to invoke code there, but child controls are not yet present. The various events required are fired some time later. With a custom control it would work. This is indeed another powerful solution. By implementing your own label you can access the constructor without needing to do anything elsewhere: lq^he__h]ooIuH]^ah6H]^ah w lq^he_IuH]^ah$% w pdeo*Patp9@]paPeia*Jks*PkHkjc@]pa$%7 y y This is a slightly modified label that simply initializes itself at the right time without any side effects. The constructor call assures that any tracking begins later.

NNote

The internal “building steps” of an object, like the constructor call, are made before the lifetime of the object begins. By “lifetime,” I mean the life of an object within the control’s or page’s life cycle—not the lifetime of an object within the runtime.

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Attaching Dynamic Controls All controls have a collection of child controls, represented by the property ?kjpnkho. Some controls, such as H]^ah, have an empty collection, because they can’t render children. All controls inherit the collection from ?kjpnkh base class. This is the common way to access the hierarchy of controls. The class behind the collection is defined: lq^he__h]oo?kjpnkh?khha_pekj6E?khha_pekj(EAjqian]^ha There are no obvious limits preventing you from adding new controls at any time. With view state, it’s not that easy. View state can track values only for existing controls. To handle dynamic controls, you need to add them on any page load, whether it’s a postback or regular page load cycle. Attaching dynamic controls must happen in the initializing phase (KjEjep event), because, at an earlier state, there is no hierarchy of controls to which you could attach anything. View state of those dynamically attached controls is then tracked automatically. Remember that this is done recursively through the whole hierarchy, so the Op]pa>]c classWILLNEVERMISSANYTHING(OWEVER THISPOINTIS critical. You might experience the following exception loading the page after postback: WB]eha`hk]`ejcreasop]paY B]eha`pkhk]`reasop]pa*Pda_kjpnkhpnaaejpksde_dreasop]paeo^aejchk]`a`iqop i]p_dpda_kjpnkhpnaapd]ps]oqoa`pko]rareasop]pa`qnejcpdalnarekqonamqaop*Bkn at]ilha(sdaj]``ejc_kjpnkho`uj]ie_]hhu(pda_kjpnkho]``a``qnejc]lkop)^]_giqop i]p_dpdapula]j`lkoepekjkbpda_kjpnkho]``a``qnejcpdaejepe]hnamqaop* Let’s create an example so that you can figure out what is happening internally: lnkpa_pa`rke`L]ca[Ejep$k^fa_poaj`an(Arajp=ncoa% w eb$EoLkop>]_g% w >qppkjiu>qppkj9jas>qppkj$%7 bkni-*?kjpnkho*=``$iu>qppkj%7 iu>qppkj*Patp9?he_gdana7 y ahoa w H]^ahh]^ah9jasH]^ah$%7 bkni-*?kjpnkho*=``$h]^ah%7 y y The intent of this code is obvious. The user has a >qppkj to invoke some action, and, when the action is completed, the button is replaced by a H]^ah control. You might argue that this is not good practice, but let’s examine it for the moment. View state tries to recognize the elements solely by their index. In this example the control at index [0] is the >qppkj. After postback it has been replaced by the H]^ah, using the same index [0]. This does not lead to the exception previously shown, because the restoring code is fairly stupid. It just looks for the right property, and both >qppkj and H]^ah share the same Patp property. While this works, the label now shows the text “Click here”. 7HY4HEEXCEPTIONAPPEARSEVENIFTHISLESS THAN IDEALMETHODFAILS PROBABLYBECAUSETHECONTROL does not provide the expected property. The first solution is simple. Turn off view state for the button control. Since you throw away the button anyway, view state is not required at all. If the view state is being saved, it can’t disturb the NEXTCYCLEˆPROBLEMSOLVED(EREISTHESOLUTIONINALLITSGLORY lnkpa_pa`rke`L]ca[Ejep$k^fa_poaj`an(Arajp=ncoa% w

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eb$EoLkop>]_g% w >qppkjiu>qppkj9jas>qppkj$%7 iu>qppkj*Aj]^haReasOp]pa9b]hoa7 bkni-*?kjpnkho*=``$iu>qppkj%7 iu>qppkj*Patp9?he_gdana7 y ahoa w H]^ahh]^ah9jasH]^ah$%7 bkni-*?kjpnkho*=``$h]^ah%7 y y (ADYOUBEENUSINGVIEWSTATEINTHEPRECEDINGSAMPLE THEPROBLEMWOULDRESOLVEITSELFˆTHAT is, if you had recreated the control after postback, which is one of the basic rules of dynamic con trols creation. The ultimate solution looks like this: lnkpa_pa`rke`L]ca[Ejep$k^fa_poaj`an(Arajp=ncoa% w >qppkjiu>qppkj9jas>qppkj$%7 iu>qppkj*Aj]^haReasOp]pa9b]hoa7 bkni-*?kjpnkho*=``$iu>qppkj%7 iu>qppkj*Patp9?he_gdana7 eb$EoLkop>]_g% w H]^ahh]^ah9jasH]^ah$%7 bkni-*?kjpnkho*=``$h]^ah%7 iu>qppkj*Reoe^ha9b]hoa7 y y (EREYOUARECLOSETOTHEBESTPRACTICE!LLOWALLCONTROLSONTHEPAGETOREMAINUNTOUCHEDAND switch the visibility on and off, as required, via code. The render method is smart enough to not ren der invisible controls. But that’s another topic and would lead us away from view state.

Initializing Dynamically Created Controls I discussed dynamic controls before and, reading the text, you might feel that there are some issues with them. This is indeed something you need to approach carefully, but there are no real issues. The problem is very similar to the one described before. Because you create the control when you choose, you have more influence and this makes your life easier. It does, however, run against the paradigm that says that you should code in a declarative way whenever possible, because you leave the world of declarative definitions completely. In any case, let’s look at how to handle another view state issue correctly. lq^he__h]ooIu?qopki?kjpnkh6?kjpnkh w lnkpa_pa`kranne`arke`?na]pa?deh`?kjpnkho$% w H]^ahh9jasH]^ah$%7 ?kjpnkho*=``$h%7 h*Patp9@]paPeia*Jks*PkHkjc@]pa$%7 y y

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You can create child controls any time, but the ?na]pa?deh`?kjpnkho method is the best opportunity for fitting into the event sequence. The initialize event is called and the control doesn’t miss the tracking of view state. The secret is the behavior of the ?kjpnkho*=`` call. This isn’t just ACOLLECTIONITDOESMUCHMOREWHENTHE=`` method is invoked. Even if all events of the parent hierarchy are complete, the control begins its regular life cycle and all events involved here are fired correctly. That means that the control starts tracking view state immediately after it’s added to the collection. ?na]pa?deh`?kjpnkho always seems too late, as even though it is called at different points in time, it’s always later than KjEjep*USTFORCOMPLETENESS YOUNEEDTOKNOWTHATITSBASED on Ajoqna?deh`?kjpnkho call, which happens in KjLnaNaj`an at the latest. For some reasons the call might come much earlier. It depends on the control’s parts being rendered due to specific condi TIONS4HISHAPPENSVIRTUALLYINDATA BOUNDCONTROLSTHATCANSHOWDIFFERENTTEMPLATESDEPENDING on actual state. Now take a closer look at the solution: lq^he__h]ooIu?qopki?kjpnkh6?kjpnkh w lnkpa_pa`kranne`arke`?na]pa?deh`?kjpnkho$% w H]^ahh9jasH]^ah$%7 h*Patp9@]paPeia*Jks*PkHkjc@]pa$%7 ?kjpnkho*=``$h%7 y y There is only a subtle difference. The control’s properties are set before the control is added, which means that it’s initialized before the KjEjep is fired, and that subsequently it has not yet begun to track the view state. You can also databind controls before they have been added to the parent control’s control hierarchy. This is very powerful and flexible. So real developers write their own custom controls and know how they work internally.

Summary In this chapter you learned about the internal processing of ASP.NET, especially the processing pipeline, which is running a single request and performs the steps required to create the content sent to the client finally. The pipeline forms the life cycle of application, pages, and controls. Dur ing the life cycle several states store current processing step’s data. To rescue data from one request to another, the view state is used. You learned what the view state is for and how to overcome the quirks and traps the implementation has. (OWEVER 7EBAPPLICATIONSHANDLEUSUALLYMORETHANONEREQUESTATATIME4HENEXTCHAPTER extends the description by looking into threading, thread pools, and other stuff required to make an ASP.NET project fast and reliable even if it comes under pressure from multiple requests.

C HAPTER

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Worker and Threads

I

n the first chapter I looked into the handling of a page request, and, in particular, the application life cycle and page life cycle. This is the fundamental process that runs when anyone requests a page resource. However, Chapter 1 was a simplification of the situation—I assumed that only one request comes in at a time. Reality is quite different. Managing hundreds, or even thousands, of simultaneous requests requires advanced knowledge and skills. In this and subsequent chapters you will learn those skills. This chapter includes:

s (OW!30.%4HANDLESMULTIPLEREQUESTS



s (OWTOMANAGETHEWORKERPROCESSESANDOPTIMIZETHEWORKLOAD



s 4HETHREADMODEL THREADPOOLBEHAVIORANDHOWTOOPTIMIZEITSUSAGE



s (OWTOBUILDASYNCHRONOUS handlers, pages, and tasks

Managing the Worker Process In Chapter 1, you learned about the worker process, w3wp.exe, which executes a request and hosts THE!30.%4ENGINE-ANAGINGTHEWORKERPROCESSISTHEKEYTOMANAGINGHIGHSERVERDEMAND AND keeping your applications stable and reliable.

Managing Worker Processes and AppDomains in IIS7 One of the leading Windows application management tools is Windows Management Instrumentation (WMI)9OUHAVEPROBABLYUSED7-)TOADMINISTERBASIC!30.%4 RELATEDPARTSOF))3)TS a well-known way to access worker processes while your application is running. 4OACCOMMODATETODAYSMANAGED CODEWORLD -ICROSOFTEXPOSEDTHE7-)AND#/-METHOD CALLSVIA.%4)NPREVIOUSPROGRAMMINGENVIRONMENTS THEACCESSTOPROPERTIESANDEVENTSOFTHE MODELSCOMPONENTSISBASEDONUNTYPEDSTRINGS LIKEcapLnklanpu$J]ia%. Instead of invoking 7-)DIRECTLY YOUCANMANAGE))3USING.%4TYPEDCLASSES RATHERTHANUSINGTHOSEUNTYPEDSTRINGS 4HESECLASSESEXPOSEADIRECTINTERFACETOTHE))3MANAGEMENTLEVELANDAPPEARTOBEEASY to use and robust.

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GOOD OLD DAYS: WINDOWS MANAGEMENT INSTRUMENTATION Windows exposes the Windows Driver Model as a framework for device drivers. Windows Management Instrumentation (WMI) is a set of extensions that provides information about and notifications from instrumented components. Programming environments and tools use WMI to access the underlying hardware components using the driver model. You can find a good introduction in Wikipedia at: dppl6++aj*segela`e]*knc+sege+Sej`kso[I]j]caiajp[ Ejopnqiajp]pekj. It suggests that WMI is a good tool for automating the management of worker processes and application domains in IIS7. It can also help us find a better way to customize the ASP.NET environment. IIS7 worker processes are spawned by the Windows Process Activation Service (WAS), using w3wp.exe. A worker process can contain AppDomains that are typically created to handle a request.

Prerequisites There areSEVERALPREREQUISITESTOWRITINGSOPHISTICATEDMANAGEMENTAPPLICATIONSUSING6ISUAL3TUDIO&IRSTOFALL ))3ITSELFISAPREREQUISITE.OOTHER7EB3ERVERCURRENTLYSUPPORTSTHESEINTERFACES To test your application, it must run with elevated privileges. If you run the development environMENTON7INDOWS6ISTA YOUMUSTLAUNCH6ISUAL3TUDIOWITH!DMINISTRATORRIGHTS!NAPPLICATION BUILTONSUCHASYSTEMRUNSWELLON7INDOWS3ERVER ASLONGASITRUNSWITH!DMINISTRATOR PRIVILEGES/NCE6ISUAL3TUDIOISRUNNINGWITHTHERIGHTACCOUNT YOUNEEDTOREFERENCETHEADMINISTRATIONASSEMBLIESINYOURPROJECT4HEREARESEVERALMANAGEDASSEMBLIESAVAILABLEINTHE))3 installation folder: 8!Sej@en!:Xouopai/.Xejaponr You will find several assemblies starting with the name “Microsoft.Web.” Depending on what YOUREPLANNINGTODO YOULLNEEDONEORANOTHER&ORTHEMOMENT JUSTREFERENCEALLOFTHEMTO ENSURETHATALLTHEEXAMPLESINTHISCHAPTERRUNPROPERLY(ERESTHELISTOFWHATYOULLNEED

s Ie_nkokbp*Sa^*=`iejeopn]pekj



s Ie_nkokbp*Sa^*I]j]caiajp*=oljap



s Ie_nkokbp*Sa^*I]j]caiajp*=oljap?heajp



s Ie_nkokbp*Sa^*I]j]caiajp



s Ie_nkokbp*Sa^*I]j]caiajp*Eeo



s Ie_nkokbp*Sa^*I]j]caiajp*Eeo?heajp

Tasks to Manage There are several tasks you can manage using the techniques described in this chapter. They will ALLOWYOUTOEXTENDTHEAVAILABLETOOLKITANDCUSTOMIZETHEMANAGEMENTOFTHE!30.%4ENVIRONment. I will focus here on some of the more common tasks, like:

s 6IEWTHECURRENTLYEXECUTINGREQUESTSFORAWORKERPROCESS



s 'ETTHESTATEOFALLWORKERPROCESSES



s 5NLOADASPECIFIC!PP$OMAIN ORALL!PP$OMAINS



s $ISPLAYALL!PP$OMAINSANDTHEIRPROPERTIES

C H A P T E R 2 N W O R K E R A N D T H R E A D S

There is almost unlimited scope for using the new management classes to extend the existing !30.%4MANAGEMENTCAPABILITIES4HISINCLUDES BUTISNOTLIMITEDTO THEFOLLOWING

s .OTIFYWHENANUNHANDLEDEXCEPTIONOCCURS



s 7ATCHLONG LASTINGREQUESTS



s 7ATCHTHENUMBEROFWORKERTHREADSANDSTATUSOFTHREADPOOL



s 0ROVIDETHENUMBEROFUSERSTHATMATCHSPECIFICCONDITIONS



s -ANAGEINTERNALSETTINGSOF!30.%4AND))3

Back Up Your Configuration It is possibleTHATTHEFOLLOWINGSAMPLESWILLDESTROYORDAMAGEYOUR))3CONFIGURATION!SITSCUMbersome to re-install your development environment after any undesirable side effects, you should TESTINAVIRTUALMACHINEORBACKUPTHE))3CONFIGURATIONOFYOURPRODUCTIONMACHINEBEFOREYOU START4HE!PP#MDTOOLISVERYUSEFULTOMAKEINSTANTBACKUPSOFTHECONFIGURATION)THASSEVERAL options. The basic structure of the command is: =ll?i`?kii]j`K^fa_pPulaE@L]n]iapan The _kii]j` parameter depends on the ObjectType parameter. For backup purposes the K^fa_pPula is >]_gql. You can use the following commands:

s LIST: shows all available backups



s ADD: creates a new backup for the current configuration



s DELETE: delete a backup from disk



s RESTORE: restore a backup and overwrite current configuration

4HEUSAGEISSTRAIGHTFORWARD!GAIN REMEMBERTORUNTHISTOOLWITH!DMINISTRATORPRIVILEGESTO ACCESSTHE))3SETTINGS To make a backup of the configuration: 1. /PENACOMMANDWINDOWWITH!DMINISTRATORRIGHTS 2. .AVIGATETO7IN$IR<SYSTEM
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Figure 2-1. Backup command and created Backup folder with IIS7 settings

Basic Tasks The code in,ISTING SHOWSTHETYPICALSTRUCTUREOFAN))3MANAGEMENTCODESNIPPET9OUCAN USEWHATEVERCLIENTENVIRONMENTYOUPREFER9OUCOULDUSEASIMPLE70&7INDOWS0RESENTATION Foundation) client to display the data in a hierarchical format (such as a PnaaReas), or perhaps well-formatted in a Ne_dPatp>kt control. For the purpose of demonstrating sample code, a console application is a simple, satisfactory alternative. I will use the following generic test structure for the listing examples. Listing 2-1. Basic Code Structure for IIS7 Administration Code Snippets qoejcOuopai7 qoejcOuopai*Patp7 qoejcIe_nkokbp*Sa^*=`iejeopn]pekj7 j]iaol]_a=lnaoo*=olJapAtpajoe^ehepu*EEO3?kjokha w op]pe__h]ooEEO3I]j]caiajp w ejpanj]hop]pe_opnejcIapdk`$% w Opnejc>qeh`ano^9jasOpnejc>qeh`an$%7

C H A P T E R 2 N W O R K E R A N D T H R E A D S

++?k`ackaodana napqnjo^*PkOpnejc$%7 y y y 4HESESTATICMETHODSAREINVOKEDFROMTHECONSOLESENTRYPOINT4HEBASISFORMOSTOPERATIONS is the Ie_nkokbp*Sa^*=`iejeopn]pekj*OanranI]j]can class. From the OanranI]j]can class there are several collections available via corresponding properties:

s 3ITES3ITE#OLLECTION



s 7ORKER0ROCESSES7ORKER0ROCESS#OLLECTION



s &ROM3ITECLASSEXPOSEDBY3ITE#OLLECTION s !PPLICATIONS!PPLICATION#OLLECTION s "INDINGS"INDING#OLLECTION



s &ORM6IRTUAL$IRECTORIESCOLLECTIONEXPOSEDBY!PPLICATIONVIA!PPLICATIONSPROPERTY s 6IRTUAL$IRECTORY6IRTUAL$IRECTORY#OLLECTION

Through these collections you can reach the desired objects and properties for monitoring ANDMANAGING))39OUALWAYSHAVEREADANDWRITEACCESS4HATMEANSYOUCANVIRTUALLYCHANGE all configuration settings programmatically available using the Management Console. To save your changes, you need to explicitly call the ?kiiep?d]jcao method.

Get Information About the Worker Processes In the next example, I show you how to loop through each worker processONA7EB3ERVER9OULL see then how to display the currently executing requests, process ID, and state of each worker process, as well as the application pool to which it belongs.

Get the State of a Worker Process The Ie_nkokbp*Sa^*=`iejeopn]pekj*SknganLnk_aoo object inTHE))3ADMINISTRATIONHASAOp]pa property that indicates whether a worker process is starting, running, or stopping. There are two more properties that particularly interest us: =llLkkhJ]ia and Lnk_aooE`. The =llhe_]pekjLkkh property represents the application pool to which the worker process belongs. The Lnk_aooE` property CONTAINSTHEPROCESS)$THATUNIQUELYIDENTIFIESTHEWORKERPROCESSTHATISANINTEGERVALUE4HE Lnk_aooCqe` methodRETURNSTHEPARTICULAR'UIDSEE,ISTING   Listing 2-2. Getting Information About Worker Processes ejpanj]hop]pe_opnejcOdksSknganLnk_aooao$% w Opnejc>qeh`ano^9jasOpnejc>qeh`an$%7 pnu w OanranI]j]cani]j]can9jasOanranI]j]can$%7 bkna]_d$SknganLnk_aoolnk_eji]j]can*SknganLnk_aooao% w o^*=llaj`Bkni]p$SknganLnk_aoobkqj`6w,yXj(lnk_*Lnk_aooE`%7 o^*=llaj`Bkni]p$Xpx))=llLkkh6w,yXj(lnk_*=llLkkhJ]ia%7 o^*=llaj`Bkni]p$Xpx))Lnk_Cqe`6w,yXj(lnk_*Lnk_aooCqe`%7 o^*=llaj`Bkni]p$Xpx))Op]pa6w,yXj(lnk_*Op]pa*PkOpnejc$%%7

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bkna]_d$=llhe_]pekj@ki]ej]ll@kiejlnk_*=llhe_]pekj@ki]ejo% w o^*=llaj`Bkni]p$ Xp'))=llhe_]pekj@ki]ejBkqj`6w,yXj(]ll@ki*E`%7 o^*=llaj`Bkni]p$ XpXpx))=ll@kiLduoL]pd6w,yXj(]ll@ki*Lduoe_]hL]pd%7 o^*=llaj`Bkni]p$ XpXp'))=ll@kiRenpL]pd6w,yXj(]ll@ki*Renpq]hL]pd%7 y y napqnjo^*PkOpnejc$%7 y _]p_d$At_alpekjat% w napqnjat*Iaoo]ca7 y y The worker processes are exposed by the property SknganLnk_aooao. The value should match the number of w3wp.exe instances running in the Windows Task Manager.

NTip

If there are no worker processes but IIS7 is running, open a Web site to force the process to launch.

4HEPROPERTIESUSEDDEPENDONTHEOBJECTYOUWISHTOINVESTIGATESEE&IGURE  2EFERTOTHE DOCUMENTATIONON-3$.TOGETFULLDESCRIPTIONSOFALLAVAILABLEVALUES3EEALSO dppl6++io`j*ie_nkokbp* _ki+aj)qo+he^n]nu+]]/03205*]olt for more details.

Figure 2-2. Watching worker processes To monitor your worker processes, check the Op]pa property. The state of a process can be one of the values defined in the SknganLnk_aooOp]pa enumeration:

s 3TARTING



s 2UNNING



s 3TOPPING



s 5NKNOWN

7HYCANTTHEWORKERPROCESSHAVEASTATEOFh3TOPPEDv!FTERTHEPROCESSHASBEENSHUTDOWN the executable is disposed of and removed from memory. The worker process then disappears from the list of processes. Therefore, the worker is first starting, then running, and, if there is nothing to DO STOPPING4HEREISNTASPECIFICSITUATIONWHERETHESTATEQjgjksj appears, as the name implies. I assume that it occurs when the process dies unexpectedly and hangs.

C H A P T E R 2 N W O R K E R A N D T H R E A D S

Get Executing Requests One excitingNEWFEATUREOF))3ISTHEABILITYTOSEETHEREQUESTSTHATARECURRENTLYEXECUTINGIN a worker process. You do this with the SknganLnk_aoo*CapNamqaopo method in a manner very similar to the one shown before. Retrieve the worker process and invoke the CapNamqaopo method to get the current requests. The CapNamqaopo method requires an ejp parameter to filter the results for requests that have run for at least the number of milliseconds specified. This is very useful for displaying only longRUNNINGREQUESTS)TSAGOODIDEATOSETTHEVALUETOZEROINITIALLYINORDERTOGETALLREQUESTS AS SHOWNIN,ISTING 

NTip

Capturing a request to test an application within the development environment can be tricky. Use the

Pdna]`*Ohaal method to make the request last long enough to be caught. Use an editor to save the following text into a file called Ohaal*]olt. The complete page for a request that will take a minute to execute: 8!Ouopai*Pdna]`ejc*Pdna]`*Ohaal$2,,,,% Naolkjoa*Snepa$E#ibej]hhubejeoda`***%!:

2UNNINGTHEMANAGEMENTCODE ASIN,ISTING  SHOWSTHATTHEREQUESTISRUNNINGANDDISPLAYSVARIOUSPROPERTIESFORTHEREQUEST4HECODEREQUIRESTHAT))3FEATURESLIKE2EQUEST-ONITOR are properly installed. This is an option you can activate in the Windows Components installation FEATUREOF3YSTEM#ONTROL0ANEL5SEInternet Information Services ° WWW Services ° Health & Diagnostics and check the Request Monitor option. Listing 2-3. Looping Through Some Properties of a Running Worker Process ejpanj]hop]pe_opnejcOdksNamqaop$% w Opnejc>qeh`ano^9jasOpnejc>qeh`an$%7 pnu w OanranI]j]cani]j]can9jasOanranI]j]can$%7 bkna]_d$SknganLnk_aoolnk_eji]j]can*SknganLnk_aooao% w bkna]_d$Namqaopnejlnk_*CapNamqaopo$,%% w o^*=llaj`Bkni]p$Namqaop6Xj%7 o^*=llaj`Bkni]p$Dkopj]ia9w,yXj(n*DkopJ]ia%7 o^*=llaj`Bkni]p$Qnh9w,yXj(n*Qnh%7 o^*=llaj`Bkni]p$Ran^9w,yXj(n*Ran^%7 o^*=llaj`Bkni]p$EL9w,yXj(n*?heajpEL=``n%7 y y napqnjo^*PkOpnejc$%7 y _]p_d$At_alpekjat% w napqnjat*Iaoo]ca7 y y

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4HECONSOLESEE&IGURE  SHOWSALLTHEREQUESTSCURRENTLYRUNNINGONAVAILABLEWORKER PROCESSES"EFORERUNNINGTHISONAPRODUCTIONSYSTEM ITWOULDBEADVISABLETOADDSOMEFILTER conditions to avoid returning an excessive number of results.

Figure 2-3. Output shows detailed information about certain requests. Monitoring requests is not particularly suited to a console application. Imagine you have some REQUESTSTHATDONTFUNCTIONASEXPECTED BUTTHEERRORSAREINFREQUENTANDNOTREPRODUCIBLE)N this situation, you could write an application to monitor a specific request and log all relevant data. When the error reappears, your log file should contain information enabling you to track down the error source.

Get Information About the Application Domains The firstTIMEAREQUESTFORAN!30.%4PAGEISRECEIVED THE))3MANAGED engine module creates an APPLICATIONDOMAIN!PP$OMAIN INMEMORY WHICH)EXPLAINEDIN#HAPTER4HE!PP$OMAINPROCESSESREQUESTSFORASPXPAGES ORANYPAGETHATUSESMANAGEDCODE5NLOADINGANDENUMERATING !PP$OMAINSISSTRAIGHTFORWARD4HISSECTIONSHOWSYOUHOWTODOBOTH5NLOADINGAN!PP$OMAIN implicitly unloads all assemblies in there. You may use this to save spaces occupied by assemblies NOLONGERREQUIRED!NOTHERREASONISTHEDISTRIBUTIONOFNEWVERSIONSOFTHERELATEDASSEMBLIES WHICHAREREQUIREDTOBEUNLOADEDFIRSTANDLOADEDAGAINAFTERANUPGRADE"ECAUSETHEUNLOADINGOF INDIVIDUALASSEMBLIESISNOTDIRECTLYSUPPORTED THEUNLOADINGOFTHE!PP$OMAINISQUITE often the only option.

Unloading a Specific AppDomain To unload a specific Ie_nkokbp*Sa^*=`iejeopn]pekj*=ll@ki]ej, you must be able to uniquely idenTIFYIT!PP$OMAINSHAVETHREEKEYPROPERTIESE`, Renpq]hL]pd, and Lduoe_]hL]pd. One of these properties should be sufficient. 4HECODESNIPPETIN,ISTING SHOWSYOUHOWTOOBTAINTHEDESIRED!PP$OMAINUSINGA ,).1QUERY4HENESTEDbnki statements form a join to retrieve the =llhe_]pekj@ki]ejo property for each running SknganLnk_aoo object. The sdana clause restricts the result to the single !PP$OMAINDEFINEDBYTHEGIVENE`. For a real-life application, this value could be a variable. You saw the OdksSknganLnk_aooaoMETHODEARLIERIN,ISTING )TSNOTREQUIRED BUT)VEINCLUDED ITHEREFORDEMONSTRATIONPURPOSESSEE,ISTING  

C H A P T E R 2 N W O R K E R A N D T H R E A D S

Listing 2-4. Retrieve Information About the Application Domains ejpanj]hop]pe_opnejcQjhk]`=ll@ki]ej$opnejcj]ia% w Opnejc>qeh`ano^9jasOpnejc>qeh`an$%7 opnejce`9+HI+S/OR?+-+NKKP7 pnu w o^*=llaj`$OdksSknganLnk_aooao$%%7 OanranI]j]cani]j]can9jasOanranI]j]can$%7 r]n]ll@ki]ejo9bnkilnk_eji]j]can*SknganLnk_aooao bnki]`_ejlnk_*=llhe_]pekj@ki]ejo sdana]`_*E`99e` oaha_p]`_7 =llhe_]pekj@ki]ej]`9]ll@ki]ejo*BenopKn@ab]qhp8=llhe_]pekj@ki]ej:$%7 eb$]`9jqhh% w ]`*Qjhk]`$%7 napqnjj]ia'qjhk]`a`7 y ahoa w napqnj_]j#pbej`'j]ia7 y y _]p_d$At_alpekjat% w napqnjat*Iaoo]ca7 y y )NCIDENTALLY THE!PP$OMAINSE` property is a path that looks like this: +HI+S/OR?+-+NKKP 4HEhvINTHEPATHLISTEDISTHESITES)$hvUSUALLYCORRESPONDSTOTHEDEFAULT7EBSITE9OU COULDFINDANYNUMBERHERE DEPENDINGONHOWMANYWEBSYOUHAVEONTHEMACHINEYOURECURrently investigating. )FYOUGENERATEALISTOFYOURSERVERS!PP$OMAINSANDTHEIRPROPERTIESFIRST YOULLFINDTHERIGHT ONEEASILYSEE,ISTING WHEREYOUEXTRACTEDTHE!PP$OMAININSTANCESFROMTHECURRENTLYRUNning worker processes). (OWEVER THEPURPOSEOFTHESCRIPTWASTOUNLOADAPARTICULAR!PP$OMAIN4OUNDERSTANDWHAT HAPPENSWHENYOUUNLOADAN!PP$OMAIN RUNTHISSCENARIO

s 2EQUESTAPAGEFROMYOURSERVER



s 7ATCHRUNNINGPROCESSESAND!PP$OMAINSANDRETRIEVETHEPROPERTIES



s ,AUNCHTHECODEANDUNLOADTHEDOMAIN



s 2EQUESTTHEPAGEAGAIN



s 2ETRIEVETHEVERYSAME information from properties.

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Unloading All AppDomains The nextEXAMPLEIN,ISTING UNLOADSALL!PP$OMAINS!GAIN )USE,).1ANDGENERICFEATURES 9OUDONTHAVETODOITTHISWAY BUTITRESULTSINCOMPACTANDHIGHLYREADABLECODE4HE,).1STATEment again uses a nested query. Listing 2-5. Unload All AppDomains ejpanj]hop]pe_opnejcQjhk]`=ll@ki]ejo$% w pnu w OanranI]j]cani]j]can9jasOanranI]j]can$%7 Bqj_8=llhe_]pekj@ki]ej(^kkh:qjhk]`Bqj_9± jasBqj_8=llhe_]pekj@ki]ej(^kkh:$Qjhk]`%7 r]n]ll@ki]ejo9bnkilnk_eji]j]can*SknganLnk_aooao bnki]`_ejlnk_*=llhe_]pekj@ki]ejo sdanaqjhk]`Bqj_$]`_%99pnqa oaha_p]`_7 napqnjQjhk]`a`']ll@ki]ejo*?kqjp$%'`ki]ej$o%7 y _]p_d$At_alpekjat% w napqnjat*Iaoo]ca7 y y lner]paop]pe_^kkhQjhk]`$=llhe_]pekj@ki]ej]ll@ki]ej% w pnu w ]ll@ki]ej*Qjhk]`$%7 napqnjpnqa7 y _]p_d w napqnjb]hoa7 y y The unload method is encapsulated in the callback function Qjhk]`)TTAKESTHE!PP$OMAIN as a parameter of type =llhe_]pekj@ki]ej!SBEFORE THEQUERYSTARTSBYRETRIEVINGTHEWORKERPROCESSESANDTHE!PP$OMAINSJOINEDTOTHEM)NTHEsdana clause, the inline method qjhk]`Bqj_$% is used to unload the domain. The Bqj_ type is a predefined typed delegate used to pass a parameter ANDRETRIEVEA"OOLEANRESULTFLAG4HECLAUSEFORCESTHEMETHODCALLTOQjhk]` and the return value DECIDESWHETHERTHE!PP$OMAINBECOMESPARTOFTHERESULTSET4HISLEADSTOADIRECTUSAGEOFTHE ?kqjp method that returns the number of successfully unloaded!PP$OMAINSSEE&IGURE  

Figure 2-4. Number of successfully unloaded AppDomains

C H A P T E R 2 N W O R K E R A N D T H R E A D S

Enumerating AppDomains Dealing with!PP$OMAINSINAMANAGEMENTENVIRONMENTOFTENSTARTSWITHSHOWINGALLAVAILABLEPROPERTIES&ORLEARNINGPURPOSESITMAKESSENSETOINVESTIGATETHE!PP$OMAINSPROPERTIES ,ISTING SHOWSHOWTOGETTHISINFORMATION4HEHELPFULPROPERTIESFORAN!PP$OMAINARE

s E`



s Renpq]hL]pd



s Lduoe_]hL]pd



s E`ha

IdRETURNSTHECURRENTINTERNAL)DOFTHE!PP$OMAIN4HERenpq]hL]pdISASDEFINEDINTHE))3 SETTINGSFORTHEROOTPATHITISUSUALLYhv5SUALLYTHEPHYSICALLOCATIONOFA7EBSITEISSAMEASTHE PATHUSEDASTHEPATHPARTOFTHE52,!VIRTUALPATHPOINTSTOALOCATIONOFCONTENTSOMEWHEREELSE ONTHE7EB3ERVEROREVENONAREMOTESERVER)FTHEREISNOVIRTUALDIRECTORYTHEVIRTUALPATHEQUALS the root (“/”). The Lduoe_]hL]pd is the full path to the application on local disk. The E`ha property ISARUNTIMEVALUE)TSDEFINEDASejpITRETURNSEITHEROR WHERETHELATTERISTHEVALUEFORANIDLE APPLICATIONDOMAINSEE,ISTING   Listing 2-6. Show Properties of AppDomains ejpanj]hop]pe_opnejcOdks=ll@ki]ejo$% w Opnejc>qeh`ano^9jasOpnejc>qeh`an$%7 pnu w OanranI]j]cani]j]can9jasOanranI]j]can$%7 r]n]ll@ki]ejo9bnkilnk_eji]j]can*SknganLnk_aooao bnki]`_ejlnk_*=llhe_]pekj@ki]ejo oaha_p Opnejc*Bkni]p$<Lduoe_]hL]pd9w,y w0yRenpq]hL]pd9w-y w0yLnk_aooE@9w.y w0yEoE`ha9w/y( ]`_*Lduoe_]hL]pd( ]`_*Renpq]hL]pd( ]`_*E`( ]`_*E`ha( Ajrenkjiajp*JasHeja%7 eb$]ll@ki]ejo*?kqjp$%99,% w o^*=llaj`$_]j#pbej`=ll@ki]ejo%7 y ahoa w bkna]_d$opnejc]`ej]ll@ki]ejo% w o^*=llaj`Heja$]`%7 y y napqnjo^*PkOpnejc$%7 y

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_]p_d$At_alpekjat% w napqnjat*Iaoo]ca7 y y 4HE,).1QUERYRETRIEVESTHEWORKERPROCESSESANDTHEATTACHED!PP$OMAINS)NTHEoaha_p clause, the string is constructed to simplify output. You can alter this clause to retrieve the specific VALUESYOUDESIRE7ITHTHIS YOUCANMONITORYOUR!30.%4ENVIRONMENTWITHYOURCUSTOMAPPLICATION WITHOUTREQUIRING)NTERNET)NFORMATION3ERVICES-ANAGER#ONSOLE ASSHOWNIN&IGURE 

Figure 2-5. Information About a Running AppDomain 9OUCANCOMPARETHISINFORMATIONWITHTHATAVAILABLEINTHE))3-ANAGER#ONSOLE/PENTHE))3 Manager Console, navigate to the site, and click on Advanced Settings on Action List to see the settings and check against the values retrieved using the code shown previously. When working with the =llhe_]pekj@ki]ej object, you might see many more properties than were shown in the last example. This is because all settings derive from the ?kjbecqn]pekjOappejco TYPE WHICHCONTAINSSEVERALCOMMONPROPERTIESTHATYOUDONTNEED !DDITIONALVALUESABOUTTHEWORKERPROCESSAREHELPFUL TOO9OUCANADDTHESEEASILYBYEXTENDing the oaha_p clause in this manner: ]`_*SknganLnk_aoo*Lnk_aooE` The object ]`_ is of the current =llhe_]pekj@ki]ejTYPE"YUSINGABACKREFERENCETOTHE SknganLnk_aoo object, all property values available there can be retrieved directly.

Configuring the Worker Process 5NLIKECLASSIC!30 WHICHRUNSINTHESAMEMEMORYSPACEAS))3 !30.%4RUNSASAPROCESSOFITS own. This gives it more flexibility, stability, and power. You can use the configuration file machine. configTOMAKETHE7EBMASTERSJOBALOTEASIER )LLTAKEACLOSERLOOKHEREATTHE!30.%4PROCESSANDTHEATTRIBUTESTHATYOUCANADJUST4HE machine.configFILEISPLAIN8-,ANDEASYTOREAD!STHENAMEIMPLIES ITSADEFINITIONATTHEMACHINE LEVEL3EVERALPORTIONSDEFINETHEDEFAULTVALUESFORTHEAPPLICATIONANDTHEFOLDER SPECIFICweb.config. (OWEVER SOMEPARTSCANTBEOVERWRITTEN ANDTHERESNOPOINTINATTEMPTINGTO alter others.

The machine.config File !SMENTIONEDEARLIER VERSIONOFTHE.%4FRAMEWORKAUGMENTS RATHERTHANREPLACES .%4 &RAMEWORK4HISEXPLAINSWHYTHEmachine.configFILEISSTOREDUNDERTHEHIVE4HEPATHON your machine should look similar to: !Sej@en!XIe_nkokbp*JAPXBn]iaskngXr.*,*1,3.3X?KJBEC

C H A P T E R 2 N W O R K E R A N D T H R E A D S

4HEREARESEVERALOTHERCONFIGURATIONFILES BUTWEREONLYEXAMININGmachine.config"ECAUSE ITS8-, YOUCANUSE6ISUAL3TUDIOTOEDITIT4HEWORKERPROCESSSETTINGSARESTOREDINTHE 8lnk_aooIk`ah: tag)TSLOCATEDUNDER8ouopai*sa^: and usually looks like this: 8lnk_aooIk`ah]qpk?kjbec9pnqa+: Microsoft sets all common values using the auto configuration option. This is good for most INSTALLATIONS BUTNOTALL4OOPTIMIZETHESETTINGS YOUCANSETTHEVALUEOFTHISATTRIBUTETOb]hoa and change whatever you like: 8lnk_aooIk`ah]qpk?kjbec9b]hoa+: However, changing basic settings is not simple and may lead to servers not responding or perFORMINGPOORLY"EFOREGOINGON LETMEEXPLAIN the various settings.

NNote

Changes made to the 8lnk_aooIk`ah: tag do not have immediate effect. You must restart a worker process to force it to re-read the settings. To restart a worker process, you can open Task Manager, right-click the w3wp.exe found in the task list, and kill the process. The worker process will start again automatically.

Why Customize the machine.config Settings? You mayWONDERWHYANDWHENYOURESUPPOSEDTOCHANGETHEmachine.config settings and the 8lnk_aooIk`ah:SETTINGS,ETSCONSIDERTHEFOLLOWINGSCENARIO

s 9OURNETWORKSUPPORTSONLYONEAPPLICATIONDOMAIN!PP$OMAIN 



s %ACHPAGECAUSESONEREQUESTNOSUBSEQUENT!*!8CALLS 



s !LLREQUESTSGOTOTHESAME)0ADDRESS

In this case, the default settings are very good and there is no reason to change anything. However, other specific scenarios could be problematic:

s 2EQUESTSTOMANY)0ADDRESSES



s &REQUENTREDIRECTS(440STATUSCODE



s 5SINGAUTHENTICATION



s 5SINGMORETHANONE!PP$OMAIN

The following section describes all the lnk_aooIk`ah parameters. (In a later section in this chapTER h#ONFIGURINGTHE4HREAD0OOL v)LLEXPLAINTHISINEVENGREATERDEPTH +EEPINMINDTHAT BEHINDTHESCENES ))3MUSTHANDLETHEAVAILABLERESOURCESTOMANAGEALL incoming requests. If the rate of incoming page requests is such that the fraction of memory in use OR#05POWEREXCEEDSCERTAINLEVELS THEDEFAULTVALUESFORTHElnk_aooIk`ah parameters may not be optimal. However, setting higher values is not always better, as this can lead to higher resource consumption and slow down even a lightly-loaded server handling simple requests. Finding the most appropriate options in the parameter jungle is a challenge.

A First Look into the Attributes ABLE LISTS the lnk_aooIk`ah attributes available. The description column indicates the purpose 4 of each attribute and where to find more information.

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Table 2-1. Settings Available for the <processModel> Tag (Excerpt)

Attribute

Default

Description

_heajp?kjja_pa`?da_g

FIVESECONDS

Once a request has been waiting in the queue FORTHISLONG !30.%4CHECKSWHETHERTHECLIent is still connected.

_lqI]og

XFFFFFFFF

3PECIFIESWHICH#05OFAMULTIPROCESSOR SYSTEMRUNS!30.%4PROCESSES4HEVALUEIS ABITMASKWHEREEACHBITREPRESENTSA#05 !SSUMEYOUSETTHEVALUETOXA WHICHIS INBINARYFORM#05SARENUMBEREDBEGINNINGWITH ANDREADFROMRIGHTTOLEFT&ORTHIS VALUE #05SANDAREQUALIFIEDTORUN!30 .%4THREADSAND#05SANDARENOT

aj]^ha

true

%NABLESORDISABLESTHEPROCESSMODEL

e`haPeia

Infinite

The period of inactivity (in time format hh:mm:ss), after which the worker process ENDS&OREXAMPLE AVALUEOFhvWILL CAUSETHEWORKERPROCESSTOSHUTDOWN minutes after the last request is concluded.) “Infinite” prevents the worker process from stopping at all.

hkcHarah

%RRORS

The quantity of errors written to the event log. #HOOSEFROMh!LL vh%RRORS vORh.ONEv

i]t=ll@ki]ejo



The number of application domains in one PROCESS4HEDEFAULTVALUE  ISTHEMAXImum allowed. Lower values are appropriate for hosting providers, for instance.

i]tEkPdna]`o



The maximum number of threads for I/O OPERATIONS COUNTEDONAPER #05BASIS-UST be greater than or equal to iejBnaaPdna]`o in 8dpplNqjpeia:SETTINGS!LLOWEDRANGEIS BETWEENAND3EETHESECTIONh5NDERSTANDINGAND5SING4HREADSvINTHISCHAPTER for more information.

i]tSknganPdna]`o



The maximum number of worker threads, COUNTEDONAPER #05BASIS-USTBE greater than or equal to iejBnaaPdna]`o in 8dpplNqjpeia:SETTINGS!LLOWEDRANGEIS BETWEENAND3EETHESECTIONh5NDERSTANDINGAND5SING4HREADSvINTHISCHAPTER for more information.

iaiknuHeiep



4HEMAXIMUMALLOWEDMEMORYSIZEASA percentage of total system memory that one WORKERPROCESSISALLOWEDTOCONSUME"EYOND this limit, a new worker process is launched and subsequent requests are redirected to this one.

iejEkPdna]`o

1

4HEMINIMUMNUMBEROF)/THREADS3EETHE SECTIONh5NDERSTANDINGAND5SING4HREADSvIN this chapter for more information.

iejSknganPdna]`o

1

The minimum number of worker threads. 3EETHESECTIONh5NDERSTANDINGAND5SING Threads” in this chapter for more information.

C H A P T E R 2 N W O R K E R A N D T H R E A D S

Attribute

Default

Description

qoanj]ia, l]ooskn`

!UTO'ENERATE

The account used to run the worker process.

lejcBnamqaj_u

Infinite

The time interval in hh:mm:ss format used to ping the worker process to get its state. If the worker process is not running, it is restarted.

lejcPeiakqp

Infinite

The time, also in hh:mm:ss format, waiting FORARESPONSETOAPINGREQUEST!FTERAPING timeout is detected, the process is restarted.

namqaopHeiep

Infinite

The number of requests a single worker PROCESSCANHANDLE"EYONDTHISVALUEANEW worker process starts.

namqaopMqaqaHeiep



The number of requests allowed in the queue. !NYREQUESTBEYONDTHISLIMITRECEIVESTHE (440ERRORh3ERVER4OO"USYvRESPONSE

naolkjoa@a]`hk_gEjpanr]h 

The time period (again in hh:mm:ss format) allowed for the worker process to respond TOAQUEUEDREQUEST!FTERTHETIMEPERIOD expires, the worker process is restarted. The default is three minutes.

naop]npMqaqaHeiep



!FTERANONSTANDARDUNEXPECTED TERMINAtion of the worker process, incoming requests are queued, waiting for the worker process to become available. The value specifies the number of requests queued.

oanranAnnknIaoo]caBeha

-

!FILEPATHEITHERABSOLUTEORRELATIVETOTHE machine.config file path) for a file containing the error message to send to the client when a fatal error occurs. If no file is present or the ATTRIBUTEISNOTSET THESTRINGh3ERVERUNAVAILable” is sent. This is the default setting.

odqp`ksjPeiakqp



The time the worker process is allowed to take when shutting the process down. If this time interval is exceeded, the worker process is forcibly terminated.

peiakqp

Infinite

)FAWORKERPROCESSISNOTRESPONDING !30.%4 launches a new one after the specific period is elapsed.

sa^C]n`aj    

False

!FLAGWHICHINDICATESTHATTHEATTRIBUTECPUMask is being used. If False (default), this MEANSTHATALL#05CORESAREAVAILABLEFOR worker processes and the operating system DECIDESWHICH#05WILLHANDLETHENEXT request.

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Additional Settings Outside the ProcessModel Tag The 8lnk_aooIk`ah: tag attributes control most of the relevant settings. However, there are more tags where you can refine the configuration. One important setting is shown in the following: 8ouopai*jap: 8_kjja_pekjI]j]caiajp: 8]``]``naoo9&i]t_kjja_pekj9-,,+: 8+_kjja_pekjI]j]caiajp: 8+ouopai*jap: This does not impact your client connections but controls the connections you make from your APPLICATIONTOOTHERSERVERS SUCHASFETCHING233FEEDSORUSING7EB3ERVICESONANOTHERSERVER4HE default for the attribute i]t_kjja_pekjIS WHICHISOBVIOUSLYTOOLOW)TMEANSYOUCANNOTMAKE MORETHANTWOSIMULTANEOUSCONNECTIONSTOAN)0ADDRESS FROMYOURWEB application. In the preceding sample theVALUEISSETTO

Specific Tasks 5SINGTHESE settings, you can perform specific tasks. The following sections explain how to use the attributes to:

s 2ECYCLETHEWORKERPROCESS



s 3HUTDOWNTHEWORKERPROCESS



s #HECKIFTHECLIENTISSTILLCONNECTED

Recycling the Worker Process !COMMON task configured in this manner is the recycling of the process. This generally improves the stability and reliability of your web application. There are five ways to recycle a process using the attributes peiakqp, namqaopHeiep, iaiknuHeiep, naolkjoa@a]`hk_gEjpanr]h, and the pair lejcBnamqaj_u/lejcPeiakqp. In the following list, they are explained one by one:

s peiakqp9046,,6,, This involves the peiakqp attribute, which simply creates a new process after the specified time interval elapses. For example, the preceding setting will start a new process after HOURS ORTWODAYS4HEFIRSTREQUESTCAUSESTHETIMERTOSTART



s namqaopHeiep9-,,,



!NOTHERWAYISTOUSETHEnamqaopHeiep attributeANDAN)NTEGERVALUE!VALUEOF WILL STARTANEWWORKERPROCESSAFTER REQUESTSHAVEBEENMADE4HISCANBEUSEFULIFYOUR WEBSERVERSPERFORMANCEDEGRADESAFTERASETNUMBEROFREQUESTS4HISCOULDHAPPENIF YOURAPPLICATIONORCOMPONENTSINITDOESNTFREEALLMEMORY



s iaiknuHeiep9/,



!THIRDWAYISTOLETYOURSYSTEMWATCHHOWMUCHMEMORYTHEPROCESSISCONSUMING)NTHE preceding example, the attribute iaiknuHeiepISSETTOOFTHETOTALSYSTEMMEMORY/NCE the limit is reached, the process is killed, a new one is created, and all existing requests are REASSIGNEDTOTHENEWPROCESS4HISISHELPFULWHENYOUHAVEAMEMORYLEAK5SUALLYYOU set this option if you have no influence on the application or parts of it, for example, if your APPLICATIONSSUFFERFROMATHIRD PARTYCOMPONENTOFTHATYOUCANTSURRENDER

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s naolkjoa@a]`hk_gEjpanr]h9,,6,.6,,



!FOURTHAPPROACHISTOUSETHEnaolkjoa@a]`hk_gEjpanr]h attribute. The time setting of two minutes will restart the process if there are requests in the queue and if there have been no responses for the last two minutes.



s lejcBnamqaj_u9,,6,,6/,



s lejcPeiakqp9,,6,,6,1

The final method for recycling the process is to use the lejcBnamqaj_u and lejcPeiakqp attributesINTANDEM4HE)3!0)EXTENSIONPINGSTHEPROCESSATTHElejcBnamqaj_u interval, and restarts it if there is no response within the lejcPeiakqp time interval.

IMPACT OF RECYCLING THE WORKER PROCESS Recycling the worker process might have an impact on current state of application and sessions. By default, you will have an “overlapping” recycle. A new worker process will be created, and will start serving new requests. The old worker process will continue serving existing requests. When all existing requests have been services, the old worker process is shut down. Your Web site should experience no down-time. The actual time it takes for the old worker process to finish servicing all requests depends on what the requests are doing. Most requests are served in a short period of time, but suppose one is performing a long-running database query that takes more time. If so, then the old worker process will hang around for a couple of seconds. Be aware that if your web application is using in-process session state, then you will lose all sessions during a recycle. Using ASP.NET you can configure your applications to use the ASP.NET session state service, or an SQL Server to store session state, in which case you will not lose session state.

Shutting Down the Process There are two ways of shutting down the worker process.

s e`haPeiakqp9,,6.,6,, The first way uses the e`haPeiakqp attribute. If the server has not served any requests for MINUTESINTHISEXAMPLE THENITAUTOMATICALLYSHUTSDOWNTHEPROCESS)FANEWREQUEST comes in, a new process is started automatically. This might be useful if you experience long periods of inactivity. The server can then handle other tasks better because there is more free memory.



s odqp@ksjPeiakqp9,,6,,6-, The second way is by using the odqp@ksjPeiakqp attribute. This is used as a last resort after the worker process tries to shut down gracefully and fails. In this case, after the time set here has passed, a low-level kill command is performed on the process to ensure its termination. This is useful in situations where the process has crashed and is no longer responding. The setting shown will force a kill after ten seconds.

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Checking Whether the Client Is Still Connected This is useful for eliminating unwanted requests from the queue.

s _heajp?kjja_pa`?da_g9,,6,,6-,



5SERSCANBECOMEIMPATIENT)FYOURWEBSERVERISSLOWTORESPONDTOTHEIRREQUESTS THEY MIGHTCLICKONTHESAMELINKMANYTIMES%VENIFONLYTHELASTREQUESTISRETURNEDTOTHEM the server will process all the previous ones. Furthermore, if the user abandons their session with your server, the queue from that user will remain. In the preceding example, the server will check each request at ten seconds intervals after it has entered the queue, to ensure that the user who made it is still connected. If he or she is not, the server discards that request. TheREQUESTISDISCARDEDALWAYSBEFOREITSPASSEDTOTHEWORKER process.

Understanding and Using Threads )N!30.%4 THREADS are like magic. Threads areWELL KNOWNANDEASYTOPROGRAMUSING.%4TECHNIQUES(OWEVER IN!30.%4 threading is handled behind the scenes and consequently regarded by some developers as unimportant. This common misunderstanding of threading can cause poor performance, unpredictable behavior, and, in the end, unreliable applications.

ASP.NET Thread Usage on IIS 4HREADINGIN!30.%4ISCOMPLICATEDBYTHEVARIOUSCHANGES-ICROSOFTAPPLIEDOVERTHEYEARSWITH EACHNEWVERSIONOF))3!SYOUSAWIN#HAPTER ))3PLAYSAMAJORPARTIN!30.%4SREQUESTPROCESSING"ECAUSEOFTHECO EXISTENCEOF))3AND))3 )WILLFIRSTEXPLAINHOWTHREADSAREHANDLEDIN ))3 ANDTHENTHECHANGESINTHREADINGINTRODUCEDWITH))3 9OUMAYALSOTHINKOFOTHERHOSTINGCAPABILITIES!30.%4SUPPORTS"ECAUSETHREADINGHAS a direct and explicit relation to multiple requests and high workload, other environments, such as 6ISUAL3TUDIOSINTEGRATED7EB3ERVER DONOTHANDLETHREADSINANYSPECIALWAYWORTHDISCUSSING 4HATSTHEREASONWHYAPPLICATIONSMIGHTBEHAVEDIFFERENTLYWHENRUNNINGINEITHER))3ORANOTHER 7EB3ERVER

Thread Usage with IIS6 %ACHREQUESTFROMTHEOUTSIDEWORLDTOTHE7EB3ERVERRUNNING!30.%4ENGINE is handed over to AN)/THREADON))34HISTHREADCOMESFROMTHE#,2#OMMON,ANGUAGE2UNTIME 4HREAD0OOL ANDRETURNSTHESTATUSh0ENDINGvTO))3(AVINGPASSEDTHEWORKONTOTHENEWTHREAD ))3ISNOWFREE to service other requests, such as requests for static resources. 4HE#,24HREAD0OOLWORKSLIKEAQUEUE)TCANADJUSTITSELFACCORDINGTOTHEACTUALWORKLOAD This means that the situation depends on the frequency of incoming requests and the ability of the processor workload to respond to each request. There are two extreme situations you need to take care of. First, you might receive many simultaneous requests that are processed quickly. In this case, THE4HREAD0OOLWILLATTEMPTTORUNONLYONEORTWOTHREADSPER#05TOENSUREAVERYLOWLATENCY (waiting time). 3ECOND YOUMIGHTRECEIVEAFEWREQUESTSWHEREONEISPROCESSORINTENSIVEANDSOMEWHAT LONG RUNNING!DDITIONALINCOMINGREQUESTSWILLCAUSEMORETHREADSTOBESPAWNEDPER#054HE processing time will always be longer in this scenario.

C H A P T E R 2 N W O R K E R A N D T H R E A D S

!QUEUEISACLEVERWAYTOAVOIDALLOCATINGALOTOFMEMORYFOREACHREQUEST BEFOREPROCESSing starts and memory-expensive objects such as DpplNamqaop are created. Keep in mind that the thread queue is in native memory and has no overhead caused by managed code components. Once a thread is ready for processing, you leave the unmanaged world and start working completely within the managed code realm. 4HE4HREAD0OOL queue is not the only way to handle a lot of incoming requests. Within each !PP$OMAINTHEREAREWAYSTOHANDLEREQUESTSTHATEXCEEDTHENUMBEROFAVAILABLETHREADS)FTHERE ISLOTOFLATENCY THE4HREAD0OOLSTARTSGROWINGANDLAUNCHESMOREACTIVETHREADS(OWEVER THERE are physical limitations; either the system runs out of threads, or the available memory restricts the number of threads.

NNote

By default the ThreadPool has a limitation of 25 worker threads per CPU and 1000 I/O completion threads.

!30.%4SETSITSOWNLIMITSTO4HREAD0OOLUSAGE)FTHISLIMITISEXCEEDED INCOMINGREQUESTSARE still handled, but another queue is now built on the application level and performance becomes significantly worse. You can control the settings with the following parameters of the 8dpplNqjpeia: tag:

s iejBnaaPdna]`o: This parameter specifies the minimum number of free threads for new REQUESTS4HATSUSEDTOASSURETHATREQUESTSTHATNEEDADDITIONALTHREADSINTERNALLYARE HANDLEDPROPERLY4HEDEFAULTVALUEIS



s iejHk_]hNamqaopBnaaPdna]`o: This parameter specifies the number of free threads for local requests. These are requests from a local host in case of child requests issued during processING4HISHELPSPREVENTDEADLOCKSCAUSEDBYRECURSIVERE ENTRIES4HEDEFAULTVALUEIS

0ERFORMANCE#OUNTERSAREWIDELYUSEDIN7INDOWSTOMONITORASYSTEMRUNNINGWITHHIGH WORKLOAD4OOBSERVETHEINTERNALBEHAVIOROFTHE4HREAD0OOL YOUCANUSETHEFOLLOWINGCOUNTER h!30.%4!PPLICATIONS<2EQUESTSIN!PPLICATION1UEUEv !NYVALUEBUTZEROSHOWSTHATTHEREISAPERFORMANCEPROBLEMONTHATSYSTEM ASITINDICATES THATTHE4HREAD0OOLHASATSOMETIMERUN out of threads.

Managing the ThreadPool 5SUALLYTHE4HREAD0OOL does not require managing, because few sites exceed the default limitations. !DDITIONALLY THE]qpk?kjbecSETTINGSALLOWTHE!30.%4ENGINETOOPTIMIZEBEHAVIORASMUCHAS POSSIBLE(OWEVER MAINTAININGAN!30.%4SYSTEMTHATISRUNNINGNEARITSLIMITSISTHEGOALOFTHIS BOOK)FYOUEXPERIENCEPERFORMANCEISSUES ITSTIMETOEXPLOREMANUALINTERVENTION4HEAUTOSETtings assume that the number of concurrently executing requestsPER#05IS!NAPPLICATIONWITH high latency might require higher values.

Thread Usage with IIS7 )N#HAPTER )DISCUSSED))3ANDINTEGRATEDMODESEVERALTIMES!S mentioned earlier, the differENCESBETWEEN))3AND))3ARESIGNIFICANTFORBASICPAGEREQUESTPROCESSING First of all, the queues built on the application level are gone, due to poor performance. The bigGESTDIFFERENCEISTHAT))3RESTRICTSTHENUMBEROFTHREADS WHILE))3RESTRICTSTHENUMBEROFREQUESTS %ACHTHREADIN))3HANDLESAREQUEST ANDTHISˆINDIRECTLYˆLIMITSTHENUMBEROFREQUESTSHANDLEDIN PARALLEL))3ISABLE DUETOTHETIGHTINTEGRATIONOF!30.%4WITHIN))3 TODIRECTLYRESTRICTTHENUMBER OFREQUESTS)TISWHENYOUEMPLOYASYNCHRONOUSPROCESSINGTHATTHISMAKESADIFFERENCE!LTHOUGHTHE processing pipeline is usually synchronous (see Chapter 1), both handlers and modules, can be set up to run asynchronously. I explain this, with examples, in Chapter 3.

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For requests that are processed synchronously, the number of threads equals the number of requests, as each request runs in a single thread. If the processing is asynchronous, the number of threads may differ from the number of requests. Imagine that an incoming request starts processINGANDISRUNNINGALONG LASTINGACTION4HETHREADISHANDEDOVERTO!30.%4 AND))3ACCEPTSTHE next incoming request. This leads eventually to more concurrently running requests than threads. !30.%4GETSTHEREQUESTASINCOMING))3)/THREAD4HE#,24HREAD0OOLISIMMEDIATELYASKED TOCREATEANDSTARTANEWTHREAD ANDTHISTHREADBECOMESRESPONSIBLEFORTHISVERYREQUEST!S QUICKLYASITSTARTS ITRETURNSWITHSTATUSOFh0ENDINGv!FTERTHIS ))3CHECKSTHENUMBEROFREQUESTS currently executing. If this value is too high, the next request is put in a process-wide global queue. This queueISINNATIVECODEWITHIN))3

Configuring the ThreadPool In the 8lnk_aooIk`ah: configuration settings are the following parameters:

s ]qpk?kjbec



s i]tSknganPdna]`o



s i]tEkPdna]`o



s iejSknganPdna]`o



s iejEkPdna]`o

4HESETTINGSFOR))3iejBnaaPdna]`o and iejBnaaPdna]`o in the dpplNqjpeia tag are still there, BUTTHEYDONOTHING4HEYARETHEREMERELYFORBACKWARDSCOMPATIBILITY"UTWHERECANYOUFINDTHE SETTINGSFOR))37ITH.%430THESETTINGSBECOMEAVAILABLE1 in web.config, as the following shows: 8ouopai*sa^: 8]llhe_]pekjLkkhi]t?kj_qnnajpNamqaopoLan?LQ9-. i]t?kj_qnnajpPdna]`oLan?LQ9, namqaopMqaqaHeiep91,,,+: 8+ouopai*sa^: The web.config settings override the settings in the Registry mentioned in the footnote. They are not values that you would change frequently. You might experiment with different quantities, but the default is usually appropriate. The current settings are a compromise between requests for static resources such as images, and dynamic resources such as aspx pages. )N#HAPTER )LLEXPLAINTHEEXTENSIBILITYCONCEPTSOFRESOURCEMANAGEMENT4HISINCLUDESTHE CREATIONOFDESIGNTIMEEXPRESSIONSTORETRIEVERESOURCES)TSPOSSIBLETOSUPPRESSCODECOMPILATION when your aspx pages consist solely of declarative markup, resources, and expressions. This is a way TOOPTIMIZEOVERALLSYSTEMPERFORMANCEUNDERPARTICULARCIRCUMSTANCES .OW YOUCOULDTRYSETTINGTHENUMBEROFTHREADSPERREQUESTTO)FYOUHAVEONLYSTATIC requests and no (or very few) dynamic ones, and if these dynamic requests are fast due to such techniques like caching, this might improve performance. Imagine that the requests are now being EXECUTEDWITHINTHE))3)/THREADANDTHATTHEREISNOHANDOVERPROCEDURETOTHE#,24HREAD0OOL Less overhead leads to faster resource processing. The opposite scenario appears when you have many heavily asynchronous operations. In this CASE THELIMITOFTHREADSMIGHTBETOOLOW)MAGINEASCENARIOYOULLPROBABLYWORKWITH!JAX enabled applications. These applications have fewer page requests but many background tasks CREATEDBY*AVA3CRIPTWEBSERVICEPAIRS4HISISHEAVILYASYNCHRONOUS ANDASINGLEWEBPAGECAN  "EFORETHEAPPEARANCEOF.%430 THESETTINGSCANBEFOUNDINTHE2EGISTRYUNDERTHEPATH (+%9?,/#!,?-!#().%<3/&47!2%<-ICROSOFT
C H A P T E R 2 N W O R K E R A N D T H R E A D S

send large numbers of such requests. If you look into browser-based Outlook clients or Word-like TEXTPROCESSINGINTERFACES YOULLSEETHATALOTOFBACKGROUNDWORKHAPPENSEVENWHENTHEUSER MERELYMOVESTHEMOUSEPOINTER3ETTINGSOFUPTOSEVERALTHOUSANDAREPOSSIBLEINORDERTOHANDLE MANYSIMPLEREQUESTS ISTHELIMIT WITHOUTMAKINGCHANGESELSEWHERE in the system.

Server Too Busy You might beWONDERINGWHENANDWHYTHEh3ERVER4OO"USYvSTATUSISSENTTOTHECLIENT4HISIS (440STATUSERRORANDAPPEARSAMONGOTHERREASONSWHENTHELIMITOFCONCURRENTREQUESTS EXCEEDSTHEDEFAULTVALUEOF  WHICHCOULDBECHANGESBYTHEnamqaopMqaqaHeiep parameter MENTIONEDBEFORE4HEACTUALVALUEISEXPOSEDBYTHEh!30.%42EQUESTS#URRENTvPERFORMANCE counter. 3EETHESECTIONh)NSTALLA0ERFORMANCE#OUNTERvFORDETAILSONHOWTOMONITORANDLOGSUCHVALues and discover what is happening to your server at any given moment.

Tune the Threading The previous explanations might discourage you from changing theSETTINGS(OWEVER THEYRE worth exploring when performance issues arise or strange errors occur. This section shows some solutions for the following error messages:

s !PROCESSSERVINGAPPLICATIONPOOLhNAMEvEXCEEDSTIMELIMITSDURINGSHUTDOWN



s 3YSTEM)NVALID/PERATION%XCEPTION4HEREARENOTENOUGHFREETHREADSINTHE4HREAD0OOL object to complete the operation.



s (TTP%XCEPTIONX 2EQUESTTIMEDOUT To solve the preceding problems, try the following:



s ,IMITTHENUMBEROFREQUESTSTHATCANEXECUTEATTHESAMETIMETOAPPROXIMATELYPER #054HISLIMITWORKSWELLFORMOSTAPPLICATIONS



s 0ERMIT7EB3ERVICECALLBACKSTOFREELYUSETHREADSINTHE4HREAD0OOL



s 3ELECTANAPPROPRIATEVALUEFORTHEi]t_kjja_pekjoATTRIBUTE"ASEYOURSELECTIONONTHE NUMBEROF)0ADDRESSESAND!PP$OMAINSTHAT are used (more details follow in the section h3ETMAXCONNECTIONv 

Tuning Task by Task This section gives some examples of how and when to change the default settings of the following values:

s MAX7ORKER4HREADS



s MIN7ORKER4HREADS



s MAX)O4HREADS



s MIN&REE4HREADS



s MIN,OCAL2EQUEST&REE4HREADS



s MAXCONNECTION



s EXECUTION4IMEOUT

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Set maxWorkerThreads and maxIoThreads !30.%4USES the following two configuration settings to limit the number of worker threads and completion threads used: 8lnk_aooIk`ahi]tSknganPdna]`o9.,i]tEkPdna]`o9.,: The i]tSknganPdna]`o attribute and the i]tEkPdna]`o attribute are implicitly multiplied by THENUMBEROF#05S)NTHEEXAMPLE THEMAXIMUMNUMBEROFWORKERTHREADSISIFYOUHAVE a dual-core processor.

Set minFreeThreads and minLocalRequestFreeThreads !30.%4ALSO contains the following configuration settings, which determine how many worker threads and completion port threads must be available to start a remote request or a local request: 8dpplNqjpeiaiejBnaaPdna]`o94iejHk_]hNamqaopBnaaPdna]`o94: If there are insufficient threads available, the request is queued until sufficient threads are FREETOHANDLETHEREQUEST4HEREFORE !30.%4WILLNOTEXECUTEMORETHANTHEFOLLOWINGNUMBEROF requests at the same time: $i]tSknganPdna]`o&jqi?LQo%)iejBnaaPdna]`o The iejBnaaPdna]`o parameter and the iejHk_]hNamqaopBnaaPdna]`o attributes are not implicITLYMULTIPLIEDBYTHENUMBEROF#05S!SSUMINGYOUHAVEFOUR#05S THEFORMULAGIVENEQUALS PARALLELREQUESTS n 

Set minWorkerThreads !30.%4ALSO contains a configuration setting for the number of worker threads to be made available immediately to service a remote request. 8lnk_aooIk`ahiejSknganPdna]`o9-: The specified number of threads that are controlled by this setting can be created at a much FASTERRATETHANWORKERTHREADSTHATARECREATEDFROMTHE#,2SDEFAULTCAPABILITIES4HESEARESTILL regular threads, but they are prepared and ready to use anytime. Requests may suddenly fill the request queue due to a slow-down on a back-end server, a sudden burst of requests from the client end, or something similar that would cause a sudden rise in the number of requests in the queue. The default value for the iejSknganPdna]`o parameter is 1. Microsoft recommends that you set the value for the iejSknganPdna]`o parameter to half of the i]tSknganPdna]`oVALUE"YDEFAULT THE iejSknganPdna]`o parameter is implicitly multiplied byTHENUMBEROF#05S

Set maxconnection The i]t_kjja_pekj attributeDETERMINESHOWMANYCONNECTIONSCANBEMADETOASPECIFIC)0 address. The setting was mentioned before, but here is a more complex scenario: 8_kjja_pekjI]j]caiajp: 8]``]``naoo9&i]t_kjja_pekj9.: 8]``]``naoo9-,*2*.,1*40i]t_kjja_pekj9.,: 8+_kjja_pekjI]j]caiajp: The i]t_kjja_pekjSETTINGAPPLIESATTHE!PP$OMAINLEVEL#ONSEQUENTLY ONLYTWOCONNECTIONSBYDEFAULT CANBEMADETOASPECIFIC)0ADDRESSFROMEACH!PP$OMAININYOURPROCESS

C H A P T E R 2 N W O R K E R A N D T H R E A D S

)NTHISEXAMPLE ALL)0ADDRESSESACCEPTTWOCONNECTIONS EXCEPTFORTHESPECIFIEDONEAT  WHICHACCEPTS

Set executionTimeout !30.%4USES the following configuration setting to limit the request execution time (in seconds): 8dpplNqjpeiaata_qpekjPeiakqp95,+: This refers to the Oanran*O_nelpPeiakqp property exposed by the DpplOanran object. If you increase the value of the ata_qpekjPeiakqp attribute, you may have to also modify the naolkjoa@a]`hk_gEjpanr]h attribute of the 8lnk_aooIk`ah: tag.

Install a Performance Counter To monitor theCURRENTWORKLOAD YOUCANUSEA0ERFORMANCE#OUNTER. Open the Reliability and Performance Monitor TOOL0ERF-ON BYENTERINGPerfMon in the Run window. Install the counter using these steps: 1. #LICKON0ERFORMANCE-ONITORINTHETREEVIEW 2. 2IGHT CLICKANDCHOOSE.EWANDTHEN$ATA#OLLECTOR3ET 3. 'IVETHECOLLECTIONANAPPROPRIATENAMESUCHASh-ONITOR))3v ANDCLICK.EXTSEE &IGURE  

Figure 2-6. Install new data collection using the Performance Monitor tool. 4. Choose a directory in which the data is to be saved. The default path is SYSTEMDRIVE<0ERF,OGS
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9OUCANNOWOPENYOURCOLLECTIONWITHINTHEOBJECTSTREEVIEWATTHELEFTANDNAVIGATETHE PATHTO2ELIABILITYAND0ERFORMANCE°$ATA#OLLECTOR3ETS°5SER$EFINED°-ONITOR))34HEREIS ADEFAULTENTRYHERENAMEDh3YSTEM-ONITOR,OGv9OUCANMODIFYTHISORADDANEWDATACOLLECTOR,ETSADDANEWONETODEMONSTRATETHEPROCESS2IGHT CLICKONTHELEAFENTRYINTHETREENAMED -ONITOR))3ANDCHOOSE.EW°$ATA#OLLECTOR!WIZARDLAUNCHESANDASKSFORANAMEANDCOLLECTIONTYPE.AMEITh))32EQUESTvANDCHOOSE0ERFORMANCECOUNTERDATACOLLECTORASTHETYPESEE &IGURE  

Figure 2-7. Add a new Data Collector. #LICKON.EXTTOADDTHECOUNTER/NTHEWIZARDSNEXTSCREEN CHOOSE!DDANDSEARCHFOR THECOUNTER)NTHELEFT HANDAREAYOULLFINDTHE!VAILABLECOUNTERSGROUP3EARCHFORTHESECTION h!30.%4!PPLICATIONvANDEXPANDIT4HELISTISSORTEDALPHABETICALLY3CROLLDOWNTOh2EQUESTS)N !PPLICATION1UEUEv)NTHEh)NSTANCESOFSELECTEDOBJECTvGROUP YOULLFINDALLAPPLICATIONS!CCEPT THEDEFAULTSELECTION??4OTAL??TOVIEWALLREQUESTS#LICK!DDAND/+4HEMONITORBEGINSTO watch the counter and saves the results in the file chosen after the counter is started. 4OVIEWTHERESULTS OPENTHEPATH2ELIABILITYAND0ERFORMANCE° Reports °5SER$EFINED° -ONITOR))3°))32EQUEST)TMIGHTTAKESOMETIMETOLOADTHERESULTS DEPENDINGONWORKLOADAND settings. There are several ways to modify the counter to bind it to specific events. For example, you could add a scheduler to run the counter at a specific time. For instance, if you experience problems BETWEENANDAMONYOURSERVER ITDOESNTMAKESENSETORUNTHETOOLTHEWHOLEDAYANDCOLLECT an unnecessarily large amount of data.

C H A P T E R 2 N W O R K E R A N D T H R E A D S

9OUCANDEFINESTOPCONDITIONSBASEDONTIMEFRAMEORTHESIZEOFTHELOGFILE9OUCANALSO launch a task when the scheduler stops. Depending on the resources of the server, you could run an APPLICATIONTHATAUTOMATICALLYANALYZESTHECONTENT SENDINGTHELOGFILETOANEMAILADDRESS ORJUST copying it to another location. 4HISSHORTDESCRIPTIONDOESNOTCOVERTHE2ELIABILITYAND0ERFORMANCE-ONITORTOOLINALLITS GLORY)TSJUSTAhTEASERvSOTHATYOUKNOWTHEREAREPOWERFULTOOLSAVAILABLETOMONITORASERVERAND find bottlenecks, failures, and performance loss easily. You can also gather hard data to confirm a problem, find a solution, and validate that your solution fixes the PROBLEM3TARTHERE reading more about the toolREGARDING7INDOWS3ERVEROPERATINGSYSTEM dppl6++pa_djap*ie_nkokbp*_ki+ aj)qo+he^n]nu+__311,4-*]opx.

Threading and Asynchronous Operations For most scenarios, the internal thread handling is well-designed and functional. However, there are situations where you reach the limits of the default settings. In particular, if a site comes under pressure from too many requests, the internal thread pool can run out of threads and the server will NOLONGERRESPONDASEXPECTED)LLDISCUSSSEVERALTECHNIQUESFOROVERCOMINGTHIS)LLCONSIDERHOW THECOMMONLANGUAGERUNTIMETHREADPOOLISUSEDBY!30.%4TOSERVICEREQUESTS ASWELLASLOOKing into the pooling mechanisms used for handlers, modules, and applications. )LLALSOSHOWTHETHREADINGUSAGEINDEPENDENTOFOTHERTECHNIQUESANDTHEASYNCHRONOUSPROcessing of requests using internal features to solve common issues.

Threading in ASP.NET To efficientlySERVICEMULTIPLECLIENTREQUESTS 7EB3ERVERSMAKEEXTENSIVEUSEOFCONCURRENCYBY launching multiple processes and spawning multiple threads to service requests. Considering the CONSTRUCTIONANDBEHAVIOROFTHE!30.%4ENGINE ITSEEMSTHATDEVELOPERSNEEDNOTCONCERNTHEMselves with threading at all, as the challenging aspects are handled internally. This is correct for most scenarios; page requests are serviced on the same thread, and a separate instance is created to service each new request. However, there are scenarios where you reach the limits of this model—as every model has limits—and need to extend the behavior. &IRSTOFALL ACLEARUNDERSTANDINGOFTHEINTERNALBEHAVIORISREQUIRED3OMEPARTSHAVEBEEN explained in the previous sections but I will repeat it from the perspective of threading. The processWIDE#,2THREADPOOLSERVICESREQUESTS4HETHREADPOOLSIZEISSETTOWORKERTHREADSAND)/ threads by default. Recall the 8lnk_aooIk`ah: settings explained already: 8lnk_aooIk`ahaj]^ha9pnqa i]tSknganPdna]`o9.1 i]tEkPdna]`o9.1+: !SEXPLAINEDIN#HAPTER FOREACHINCOMINGREQUESTANINSTANCEOFTHETYPEDppl=llhe_]pekj is CREATED4OAVOIDREALLOCATINGAPPLICATIONSANDMODULES EACH!PP$OMAINHOLDSAPOOLOFAPPLICATIONINSTANCESAND(440MODULES4HESIZEOFTHISPOOLISALSOˆTHATMEANSTHATREQUESTSCAN be handled per worker process.

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The Need for Asynchrony )MAGINETHATYOUNEEDTOEXCLUSIVELYREQUESTARESOURCE!SLONGASONEPERSONISUSINGANAPPLIcation, this is not a problem. However, web applications are typically employed by many, if not thousands, of concurrent users. The thread pool and thread handling design allows several requests TOBEEXECUTEDINPARALLELTOIMPROVETHEUSERSEXPERIENCEWHENUSINGAWEBAPPLICATION,IMITING THENUMBEROFTHREADSISIMPORTANTINORDERTOALLOWMORETHANONEREQUESTPER#05ORCORE#REATing a vast number of threads can cause a system to a grind to a halt. (OWEVER AREQUESTCANLAUNCHDIFFERENTKINDSOFTASKS0ROCESSINGAPAGEANDSENDING RESOURCESTOTHECLIENTISTHEMOSTCOMMONACTION2EQUESTINGDATAFROMADATABASE 233FEED OR 7EB3ERVICEISANOTHER2EQUESTINGDATACANBETIMECONSUMING RATHERTHANPROCESSORINTENSIVE 7HATHAPPENSTHEN4HENUMBEROFTHREADSINTHETHREADPOOLQUICKLYREACHESITSLIMITANDSUBSEQUENTREQUESTSARENOTHANDLEDASEXPECTED$ESPITETHIS THE#05ISONLYIDLING!SYOULEARNEDIN THEPREVIOUSSECTIONS THESETTINGSALLOWYOUTOCHANGETHENUMBEROFCONCURRENTTHREADS"UTTHIS is not a solution either, as your system has to handle both kinds of requests: short-lived requests for resources and long-running queries against other servers. 4OMAKETHINGSCLEARER LOOKAT,ISTING )TDELAYSAREQUESTWHILEDEMANDINGLITTLEFROMTHE #05)TDISPLAYSTHETHREAD)$TOSHOWWHETHERORNOTANEWTHREADISCREATEDTOHANDLETHEREQUEST Listing 2-7. A Simple Page That Slows Down a Request 8!<L]caH]jcq]ca9?!: 8!<EilknpJ]iaol]_a9Ouopai*Nabha_pekj!: 8!<EilknpJ]iaol]_a9Ouopai*Pdna]`ejc!: 8o_nelpnqj]p9oanran: lnkpa_pa`rke`L]ca[Hk]`$k^fa_pon_(Arajp=ncoa% w Pdna]`*Ohaal$/,,,%7 Naolkjoa*Kqplqp*Snepa$OhksNaolkjoa(Pdna]`E@9w,y(± =ll@ki]ej*Cap?qnnajpPdna]`E`$%%7 y 8+o_nelp: To test it, open the page in a browser. Open the page in more browser windows and refresh all THEPAGESWITHINTHETHREE SECONDMILLISECOND PERIOD9OULLSEETHATTHETHREAD)$EXPOSED by the script changes for each request. Once the period is over, the next request receives a recycled THREADFROMAPREVIOUSREQUEST3EVERALLONG RUNNINGREQUESTSCANFILLTHETHREADPOOLANDEASILY REACHTHELIMITOFCONCURRENTTHREADS Removing the OhaalCALL,ISTING  WILLRESULTINAFASTERRUNNINGPAGE9OUWONTBEABLETO request the page again while the server is handling the previous one. The thread IDs demonstrate that ALLREQUESTSRUNONTHESAMETHREADANDTHETHREADPOOLISNEVERFILLEDUPTOITSLIMITSEE,ISTING   Listing 2-8. A Simple Page That Performs Well (Threading/FastThread.aspx) 8!<L]caH]jcq]ca9?!: 8!<EilknpJ]iaol]_a9Ouopai*Nabha_pekj!: 8o_nelpnqj]p9oanran: lnkpa_pa`rke`L]ca[Hk]`$k^fa_pon_(Arajp=ncoa% w Naolkjoa*Kqplqp*Snepa$B]opNaolkjoa(Pdna]`E@9w,y( =ll@ki]ej*Cap?qnnajpPdna]`E`$%%7 y 8+o_nelp:

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Microsoft offers a stress test tool for simulating multiple concurrent requests even in the develOPMENTENVIRONMENT3EETHESIDEBARABOUTTHE7EB3TRESS4OOLFORMOREINFORMATION

WEB STRESS TOOL The web application stress tool can be downloaded from: dppl6++sss*ie_nkokbp*_ki+`ksjhk]`o+`ap]eho* ]olt;b]iehue`9a._,141]),2.])0/5a)]23`)31]45]]/2051"`eolh]uh]jc9aj. Unfortunately, the tool is quite old and Microsoft has not refreshed it to support newer environments. So if you run it on Vista, a DLL named msvcp50.dll is missing. You may find the file on the Web or you can safely copy it from the support files section provided with this book. Perform these steps to install the stress test tool: s $OWNLOADTHESETUPEXEFROMTHEADDRESSPREVIOUSLYSHOWN s $OWNLOADMSVCPDLLFROMTHE!PRESSSUPPORT7EBSITE s #OPYTHEUNZIPPEDFILETOFOLDER7IN$IR<SYSTEMYOUMUSTRUNWITHHIGHERPRIVILEGESTODOTHIS .OTETHAT this is really system, not system32! s )NSTALLTHESTRESSTESTTOOL s 2UNITONCETOCHECKTHATITSWORKING3TARTITASAN!DMINISTRATOR Now you can use the tool as outlined in the following sections. 4HEREAREFEWALTERNATIVETOOLSOUTTHEREYOUMIGHTCONSIDERFORYOUROWNSTRESSTESTING3EE!LIK,EVINS7#!4 at dppl6++^hkco*io`j*_ki+]hegh+]n_dera+.,,4+,/+,5+opnaoo)paop)]ol)jap)sa^)]llhe_]pekj)sepd) bnaa)s_]p)pkkh*]oltknpdaBe``han=``)ejjaTlanp(]r]eh]^ha]pdppl6++sss*ie_nkokbp*_ki+ `ksjhk]`o+`ap]eho*]olt;b]iehue`91531`]1.)4_a2)04^`)5^/_)312]2.1,.0^^"`eolh]uh]jc9aj.

Working with the Stress Test Tool !STRESSTEST is what the name implies—your application is forced to handle as many requests as NECESSARYTOFEELSTRESSED4OWALKTHROUGHTHISSTRESSTEST YOULLNEEDTOSETUPTHEPAGESPREVIOUSLY SHOWNSEE,ISTINGS AND LATERINTHISCHAPTER WITHINYOUR))3ENVIRONMENT WHICHYOUREABLE to run from a browser manually. Follow these steps to set up the script in the stress test tool. I have SET))3TOUSETHISPATH dppl6++hk_]hdkop+Pdna]`ejc+OhksPdna]`*]olt dppl6++hk_]hdkop+Pdna]`ejc+B]opPdna]`*]olt First, set up the script by adding the content tree—the pages requested from the tool (see &IGURE   4HECONTENTTREEALLOWSYOUTOSETTHEACTIONSTHETOOLPERFORMSSEVERALTIMES!LTERNATIVELY you can record a session to save the page load action. However, in this script, only one page is called USINGA'%4COMMAND SORECORDINGISNOTNECESSARY 4HESETTINGSDEFINEHOWTHETOOLOPERATESONTHESERVER)N&IGURE  )SETTHREADS WHICH CREATECONCURRENTREQUESTS4HISRUNSFORSECONDSASQUICKLYASPOSSIBLE4HEREISNOTHROTTLING ANDNOOTHEROPTIONSAREUSED4HISISTHECONFIGURATIONTHATSHOULDCAUSETHESERVERTOCREATE threads and bring the thread pool to its limit.

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Figure 2-8. Set the content for a stress test.

Figure 2-9. Settings used to force the test

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4ABLE SHOWSTHERESULTSOFSOMESTRESSTESTS2EMEMBERTHATTHEREISAWIDERANGEOFPOSsible values for response time, depending on your machine, its configuration, and what other APPLICATIONSANDSERVICESARECURRENTLYRUNNING)TSTHERELATIVEVALUESTHATARESIGNIFICANTHERE Table 2-2. Test Results Using a Web Stress Test Tool

Threads

File

Hits

Average Response Time



&AST4HREADASPX



MS



&AST4HREADASPX



MS



3LOW4HREADASPX



 MS



3LOW4HREADASPX



 MS



"OTHSEETHEFOLLOWING



 MS&AST4HREADASPX

These results are not surprising. The server is less able to handle the requests as the number OFPARALLELTHREADSINCREASES"ECAUSEWEREFORCING))3TOQUEUETHEREQUESTS THISCAUSESADDITIONALOVERHEAD2UNNINGTHECLIENTAGAINSTBOTH&AST4HREADASPXAND3LOW4HREADASPX HOWEVER INCREASESTHEAVERAGERESPONSETIMEFOR&AST4HREADASPXREQUESTSTOSECONDSANDONLYHITS BEINGHANDLED&OR3LOW4HREADASPX THENUMBEROFTHREADSMAKESNOSIGNIFICANTDIFFERENCE4HISIS the worst case—because of long-running requests, fast ones are not served quickly. Increasing the #05POWERWILLNOTHELP4HESLOWPAGEDOESNOTCONSUMEANY#05POWERBECAUSETHEREISNOTHING TOCALCULATE4HEDELAYYOUSEEISDUETOTHESATURATIONOFTHETHREADPOOL%VENTHEFASTREQUESTSARE queued until a thread is released. This demonstrates that some pages can influence the performance of other requests even if THEYHAVENOTHINGTODOWITHEACHOTHER7HATISTHESOLUTION )DISCUSSEDPREVIOUSLYTHEVARIOUSSETTINGSAVAILABLEFORIMPROVINGTHESYSTEMSBEHAVIOR)NTHE STRESSTEST)USEDTHREADS)NCREASINGTHETHREADPOOLLIMITSMIGHTHELP(OWEVER THEREALWORLD does not have a defined number of requests regularly arriving. Finding the right value is anything but easy. It could change depending on user behavior, server settings, network connection, and application code—which means that there is no right answer. 4HESOLUTIONWERELOOKINGFORSHOULDFREETHETHREADSINTHETHREADPOOLTOHOLDTHEUTILIZATION low and have enough threads available at any time. In other words, each page should behave like a fast-running page. This brings us to asynchronous handlers.

NNote

Chapter 3 is dedicated to the world of handlers and modules. Here I discuss only the portion directly related to threading issues. For more information about handlers, refer to the next chapter.

Custom Thread Pool and Asynchronous Handlers 7HILEMOST!30.%4PAGESANDHANDLERSARESERVICEDSYNCHRONOUSLYON threads drawn from the thread pool, it is possible to create handlers and pages that service requests asynchronously. !SYNCHRONOUSHANDLERSIMPLEMENTTHEEDppl=ouj_D]j`han interface, which derives from EDpplD]j`hanSEE,ISTING  

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Listing 2-9. Definition of the IHttpAsynchHandler Interface lq^he_ejpanb]_aEDppl=ouj_D]j`han6EDpplD]j`han w E=ouj_Naoqhp>acejLnk_aooNamqaop$Dppl?kjpatp_pt( =ouj_?]hh^]_g_^( k^fa_pk^f%7 rke`Aj`Lnk_aooNamqaop$E=ouj_Naoqhp]n%7 y The interface follows the typical pattern for asynchronous actions—it has a method for indicating the beginning and one for indicating the end of a process. Handlers must have a method named Lnk_aooNamqaop due to the implemented EDpplD]j`han interface. Instead of calling this method, the asynchronous handler calls the >acejLnk_aooNamqaop method. In this method, you launch a new thread and manage things, which can take some time. The method returns immediately, providing a reference to an E=ouj_NaoqhpINSTANCE4HISFREESTHETHREADFROMTHETHREADPOOL!NEWTHREAD is then used to perform the long-running action. When the internal (or private) thread returns, the Aj`Lnk_aooNamqaop method is called. The E=ouj_Naoqhp instance is handed over in order to paramETERIZETHECALL#LEANUPACTIONS SUCHASCLOSINGADATABASECONNECTION AREBESTPLACEDHERE

Asynchronous Handler with a Delegate Creating an asynchronous handler with a delegate is the most common approach. Delegates called with >acejEjrkgaIMPLICITLYCREATEANEWTHREADSEE,ISTING   Listing 2-10. A Handler Using IHttpAsyncHandler 8!<Sa^D]j`hanH]jcq]ca9??h]oo9=lnaoo*Pdna]`ejc*=ouj_D]j`hano*=ouj_D]j`han!: qoejcOuopai7 qoejcOuopai*Sa^7 qoejcOuopai*Pdna]`ejc7 qoejcOuopai*@e]cjkope_o7 qoejcOuopai*Nabha_pekj7 j]iaol]_a=lnaoo*Pdna]`ejc*=ouj_D]j`hano w lq^he_`ahac]parke`Lnk_aooNamqaop@ahac]pa$Dppl?kjpatp_pt%7 lq^he__h]oo=ouj_D]j`han6EDppl=ouj_D]j`han w lq^he_rke`Lnk_aooNamqaop$Dppl?kjpatp_pt% w Ouopai*Pdna]`ejc*Pdna]`*Ohaal$.,,,%7 _pt*Naolkjoa*Kqplqp*Snepa$ =ouj_@ahac]pa(Pdna]`E@9w,y( =ll@ki]ej*Cap?qnnajpPdna]`E`$%%7 y lq^he_^kkhEoNaqo]^ha w capwnapqnjpnqa7y y

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lq^he_E=ouj_Naoqhp>acejLnk_aooNamqaop$Dppl?kjpatp_pt(± =ouj_?]hh^]_g_^(± k^fa_pk^f% w Lnk_aooNamqaop@ahac]palnc9jasLnk_aooNamqaop@ahac]pa$Lnk_aooNamqaop%7 napqnjlnc*>acejEjrkga$_pt(_^(k^f%7 y lq^he_rke`Aj`Lnk_aooNamqaop$E=ouj_Naoqhp]n% w y y y #ALLTHISHANDLERBYUSINGABROWSER ASBEFORE TOTESTTHATITSRUNNINGPROPERLY4HEFOLLOWING 52,ASSUMESTHATYOUHAVETHEPROJECTCONFIGUREDIN))3USINGAVIRTUALDIRECTORYNAMEDh4HREADing”: dppl6++hk_]hdkop+Pdna]`ejc+=ouj_Pdna]`@ahac]pa*]odt The process starts with the method >acejLnk_aooNamqaop5SINGTHEDELEGATEANDITS >acejEjrkga method, the method Lnk_aooNamqaop is called. Then the Ohaal method simulates SOMETHINGLONGRUNNINGWITHOUTPERFORMINGANYTHINGONTHE#05"ECAUSETHEREISNOTHINGTO clean up, no code is required in Aj`Lnk_aooNamqaop. .OWITSTIMETOSEEWHATTHESTRESSTESTTOOLISREPORTING If you run the test as before, you can see that the results are nearly identical. What is going on HERE7HYWRITEASYNCHRONOUSDELEGATESIFTHEREISNOSPEEDIMPROVEMENTATALL4HEREASONISIN THEWAY!30.%4INTERNALLYHANDLESTHETHREADING Recall that when I first introduced the term “thread pool,” it was called a “process wide thread pool.” The asynchronous handler still runs in the very same process, which leads to a lack of improvement. The original thread is freed, but the new one is taken from the same thread pool. The same thing would happen if you used Pdna]`Lkkh*MqaqaQoanSkngEpai from the Ouopai*Pdna]`ejc namespace. You need to find from what other thread source you can get a new thread.

Asynchronous Handler with Custom Threads "EFOREYOUCANIMPLEMENTTHEWHOLESOLUTION ANOTHERINTERFACEISREQUIREDˆE=ouj_dNaoqhp—as the RETURNRESULTISNOWESSENTIAL4HEDEFINITIONISSHORTˆJUSTFOURPROPERTIESSEE,ISTING   Listing 2-11. The Definition of IAsyncResult lq^he_ejpanb]_aE=ouj_Naoqhp w lq^he_k^fa_p=ouj_Op]pawcap7y lq^he_^kkh?kilhapa`Ouj_dnkjkqohuwcap7y lq^he_^kkhEo?kilhapa`wcap7y lq^he_S]epD]j`ha=ouj_S]epD]j`hawcap7y y Our actual implementation of the E=ouj_dNaoqhp interface,ISTING  HASTWOADDITIONAL properties: a reference to the Dppl?kjpatp object, and a reference to the callback object. The callback method is invoked later, when processing is complete. The =ouj_Op]pa object is optional; you can use it to store private data. =ouj_S]epD]j`ha returns a S]epD]j`ha object, which is used to signal WHENTHEREQUESTISCOMPLETE5SINGTHE?kilhapaNamqaop method implemented additionally to the requirements of the interface, the calling class can execute the Aj`Lnk_aooNamqaop method. In this

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routine, the S]epD]j`haOBJECTISTRIGGERED%ITHERWAY THEEo?kilhapa` property shows that the object has reached the completed state. Listing 2-12. The Implementation of IAsyncResult (from AsyncThreadCallback.ashx) _h]oo=ouj_NamqaopOp]pa6E=ouj_Naoqhp w ejpanj]hDppl?kjpatp[_pt7 ejpanj]h=ouj_?]hh^]_g[_^7 ejpanj]hk^fa_p[`]p]7 lner]pa^kkh[eo?kilhapa`7 lner]paI]jq]hNaoapArajp[_kilhapaArajp7 lq^he_=ouj_NamqaopOp]pa$Dppl?kjpatp_pt(± =ouj_?]hh^]_g_^(± k^fa_p`]p]% w [_pt9_pt7 [_^9_^7 [`]p]9`]p]7 y ejpanj]hDppl?kjpatp?qnnajp?kjpatp w cap w napqnj[_pt7 y y ejpanj]hrke`Aj`Namqaop$% w [eo?kilhapa`9pnqa7 hk_g$pdeo% w eb$[_kilhapaArajp9jqhh% [_kilhapaArajp*Oap$%7 y ++ejrkganaceopana`_]hh^]_g(eb]ju eb$[_^9jqhh% [_^$pdeo%7 y lq^he_k^fa_p=ouj_Op]pa w cap w napqnj$[`]p]%7 y y  lq^he_^kkh?kilhapa`Ouj_dnkjkqohu w cap w napqnj$b]hoa%7

C H A P T E R 2 N W O R K E R A N D T H R E A D S

y y  lq^he_^kkhEo?kilhapa` w cap w napqnj$[eo?kilhapa`%7 y y  lq^he_S]epD]j`ha=ouj_S]epD]j`ha w cap w hk_g$pdeo% w eb$[_kilhapaArajp99jqhh% [_kilhapaArajp9jasI]jq]hNaoapArajp$b]hoa%7 napqnj[_kilhapaArajp7 y y y y The next step is to spawn a new thread to process the request. The method called on this new thread will need access to the state cached in the =ouj_NamqaopOp]pa class previously shown. To pass NECESSARYDATATOTHISOBJECT APARAMETERIZEDTHREADISUSED BASEDONL]n]iapaneva`Pdna]`Op]np class. The handler itself is similar to the one already introduced. The definition for the ashx page looks like this: 8!<Sa^D]j`hanH]jcq]ca9?± ?h]oo9=lnaoo*Pdna]`ejc*=ouj_D]j`hano*?qopki=ouj_D]j`han!: The Lnk_aooNamqaop method must be present, as it is required by the interface EDppl=ouj_D]j`han, BUTYOUDONTUSEIT4HEWHOLEWORKISSPLITBETWEENTHE>acejLnk_aooNamqaop and Aj`Lnk_aooNamqaop methods. In the >acejLnk_aooNamqaop method the =ouj_NamqaopOp]pa object is created, along with the REFERENCETOTHECONTEXTANDCALLBACKSEE,ISTING   Listing 2-13. The Implementation of AsyncResult (AsyncThreadCallback.ashx) lq^he__h]oo?qopki=ouj_D]j`han6EDppl=ouj_D]j`han w lq^he_rke`Lnk_aooNamqaop$Dppl?kjpatp_pt% w ++jkpqoa` y lq^he_^kkhEoNaqo]^ha w capwnapqnjb]hoa7y y lq^he_E=ouj_Naoqhp>acejLnk_aooNamqaop$Dppl?kjpatp_pt(± =ouj_?]hh^]_g_^(± k^fa_pk^f%

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w =ouj_NamqaopOp]panamOp]pa9± jas=ouj_NamqaopOp]pa$_pt(_^(k^f%7 L]n]iapaneva`Pdna]`Op]nppo9jasL]n]iapaneva`Pdna]`Op]np$Lnk_aooPdna]`%7 Pdna]`p9jasPdna]`$po%7 p*Op]np$namOp]pa%7 napqnjnamOp]pa7 y lq^he_rke`Aj`Lnk_aooNamqaop$E=ouj_Naoqhp]n% w =ouj_NamqaopOp]pa]no9]n]o=ouj_NamqaopOp]pa7 eb$]no9jqhh% w ]no*?qnnajp?kjpatp*Naolkjoa*Snepa$Aj`Namqaopna]_da`%7 y y lner]parke`Lnk_aooPdna]`$k^fa_pk^f% w Pdna]`*Ohaal$.,,,%7 =ouj_NamqaopOp]pa]on9k^f]o=ouj_NamqaopOp]pa7 ]on*?qnnajp?kjpatp*Naolkjoa*Kqplqp*Snepa$± =ouj_Pdna]`(Pdna]`E@9w,y(± =ll@ki]ej*Cap?qnnajpPdna]`E`$%%7 ++oecj]haj`kblnk_aooejc ]on*Aj`Namqaop$%7 y y ,ETSLOOKATTHECODETOUNDERSTANDHOWITSWORKING&IGURE SHOWSTHETHREADUSAGEDURing internal processing. Initiated by the request, the process starts by calling the >acejLnk_aooNamqaop method. The =ouj_D]j`han creates the helper objects required and launches the new custom thread independent of the thread pool. The custom thread runs and the thread pool thread is released. Once the process is completed, the end is signaled via the callback method and the request is finished. The response held in memory is waiting for the thread to complete. This might seem disapPOINTING BECAUSEITDOESNTMAKEANYTHINGFASTER4HEPAGEISSTILLWAITINGFORTHESLOWOPERATION to finish, and so is the user. Remember the thread pool issue, however; once the pool runs out of threads, the performance of the whole server is reduced and no more requests are handled properly. The advantage of custom threads is not a faster response for one user but for all users. )NSTEP ASSHOWNIN&IGURE  THECALLTOAj`Namqaop indicates the end of the process and terminates the request. Once called, the response is complete and sent to the browser. This means that you can add content to the response at any time before the Aj`Lnk_aooNamqaop method is called. )NTHEEXAMPLECODE,ISTING  THENaolkjoa*Kqplqp*Snepa method demonstrates this. 2UNTHESTRESSTESTAGAINTOSEEWHETHERYOUFINDANIMPROVEMENT5NDERPRESSUREITPERFORMS better, and the thread pool no longer runs out of threads. This allows the site to accept incoming REQUESTSATANYTIME ANDTHEWHOLESERVERAPPEARSTOBEMORERESPONSIVE!GAIN THE processing time for a single page is the same.

C H A P T E R 2 N W O R K E R A N D T H R E A D S

Figure 2-10. First step of the processing using an asynchronous handler

Figure 2-11. Second step of the processing using an asynchronous handler

Creating a Custom Thread Pool This techniqueISUSEFULFORMANYEXTENSIBILITYPROJECTS)N#HAPTER )LLSHOWMOREEXAMPLES OFPRACTICALIMPLEMENTATIONSTHATSOLVECOMMONISSUES!LLHANDLERSEXPLAINEDTHEREUSESIMPLE synchronous operations. You can implement them all as asynchronous counterparts using the TECHNIQUESDESCRIBEDHERE5SINGASYNCHRONOUSHANDLERS YOULLSEEHOWTOIMPROVETHEOVERALLPERFORMANCEOFAN!30.%4SITEDRASTICALLY4HETHREADISSUESANDHANDLERSTHAT)DISCUSSHEREAREJUST one solution. There is another issue that can be found easily using the stress test tool. In one of the previous paragraphs I wrote “accept incoming requests at any time.” This is quite a claim, as it assumes that the server will respond no matter how many requests arrive, just by creating new threads. However,

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THEOPERATINGSYSTEM #05POWER AVAILABLEMEMORY ANDARCHITECTURALRESTRICTIONSOFTHEHARDWARE may stop the code from creating new threads. It is possible for too many threads to be created, in which case they will block each other and make the system slow and unresponsive. 9OUMIGHTASKh7HYNOTUSEATHREADPOOLv5NFORTUNATELY .%4HASONLYONETHREADPOOL INTERNALLYANDITISUSEDBY!30.%44HATSWHYUSINGPdna]`Lkkh*MqaqaQoanSkngEpai does not WORK/URTASKNOWISTHECREATIONOFOUROWNTHREADPOOL3EVERALPEOPLEHAVEDONETHISSUCcessfully. Mike Woodring wrote a version which is useful and fits our needs, using the code in an asynchronous handler. The original version can be found on his page: dppl6++sss*^a]n_]jukj*_ki+. I have adapted his code to suit our needs for a handler. There are several clever aspects to this code. The usage of Dppl?kjpatp is much simpler. In the previous example, a reference to the context object was stored and the use of Dppl?kjpatp*?qnnajp was forbidden. It is not good programMINGPRACTICETOCHANGEWELL KNOWNMETHODCALLS!PARTFROMTHISEXAMPLETHEREARESEVERALOTHER IMPLEMENTATIONSOUTTHERETHATMIGHTHELPASWELL!LTERNATIVELYYOUMAYHAVEALOOKAT*ON3KEETS #USTOM4HREAD0OOLTHATSPARTOFHISh-ISCELLANEOUS5TILITY,IBRARYvdppl6++sss*uk`]*]n]_douo*_ki+ _od]nl+ieo_qpeh+ (OWEVER THECUSTOMTHREADPOOLEXPLAINEDHEREISJUSTANEXAMPLEOFWHERE!30.%4EXTENSIbility approaches can go and how to deal with very specific conditions.

Overview !CUSTOMTHREADPOOLISNOTATRIVIALPIECEOFCODE)TCONSISTSOFSEVERALCLASSES DELEGATES ANDAN interface as well. First, have a look at the types defined in the project:

s #USTOM4HREAD0OOL



s )7ORK2EQUEST



s 7ORK2EQUEST



s 4HREAD)NFO



s 4HREAD7RAPPER

4HE#USTOM4HREAD0OOLCLASS is the core implementation. It supports a bunch of characterisTICS!PARTFROMTHEFEATURESPROVIDEDBYTHE#,2STHREADPOOL THOSEARETHECRUCIALONES

s )TCANBEEXPLICITLYSTARTEDANDSTOPPEDANDRESTARTED 



s )THASCONFIGURABLETHREADPRIORITY



s )THASCONFIGURABLEFOREGROUNDBACKGROUNDCHARACTERISTIC



s )THASCONFIGURABLEMINIMUMTHREADCOUNTCALLEDhSTATICvORhPERMANENTvTHREADS 



s )THASCONFIGURABLEMAXIMUMTHREADCOUNTTHREADSADDEDOVERTHEMINIMUMARECALLED “dynamic” threads).



s )THASCONFIGURABLEDYNAMICTHREADCREATIONTRIGGERTHEPOINTATWHICHTHEPOOLDECIDESTO add new threads).



s )THASCONFIGURABLEDYNAMICTHREADDECAYINTERVALTHETIMEPERIODAFTERWHICHANIDLE dynamic thread will exit).



s )TSUPPORTSCONFIGURABLELIMITOPTIONAL TOTHEREQUESTQUEUESIZEBYDEFAULTUNBOUNDED 



s 4HEPOOLEXTENDS7AIT(ANDLETHATBECOMESSIGNALEDWHENLASTTHREADEXITS



s /PERATIONSENQUEUEDTOTHEPOOLARECANCELLABLE



s %NQUEUEOPERATIONSUPPORTSEARLYBOUNDAPPROACHLIKETHEPdna]`Lkkh*MqaqaQoanSkngEpai type) as well as late bound approach (like the ?kjpnkh*Ejrkga/>acejEjrkga approach) to posting work requests.

C H A P T E R 2 N W O R K E R A N D T H R E A D S



s /PTIONALPROPAGATIONOFCALLINGTHREADCALLCONTEXTTOTARGET



s /PTIONALPROPAGATIONOFCALLINGTHREADPRINCIPALTOTARGET



s /PTIONALPROPAGATIONOFCALLINGTHREADDppl?kjpatp to target.



s )THASSUPPORTFORSTARTEDSTOPPEDEVENTSUBSCRIPTIONANDNOTIFICATION This all makes it a well-designed tool to extend the thread pool behavior where necessary.

The Implementation of the Custom Thread Pool The next code listings show the implementation in several steps. The core functionality is explained IN LINESEE,ISTING   Listing 2-14. The Basic Thread Pool Implementation lq^he_oa]ha`_h]oo?qopkiPdna]`Lkkh6S]epD]j`ha w ++@ab]qhpl]n]iapano ++@a_]upeiaejioi]`akbiejqpao&oa_&io _kjopejp@AB=QHP[@UJ=IE?[PDNA=@[@A?=U[PEIA91&2,&-,,,7 ++iehheoa_kj`o _kjopejp@AB=QHP[JAS[PDNA=@[PNECCAN[PEIA91,,7 _kjopPdna]`Lneknepu@AB=QHP[PDNA=@[LNEKNEPU9Pdna]`Lneknepu*Jkni]h7 ++qj^kqj`a` _kjopejp@AB=QHP[NAMQAOP[MQAQA[HEIEP9)-7 lq^he_?qopkiPdna]`Lkkh$ejpejepe]hPdna]`?kqjp(ejpi]tPdna]`?kqjp(± opnejclkkhJ]ia% 6pdeo$ejepe]hPdna]`?kqjp(i]tPdna]`?kqjp(lkkhJ]ia( @AB=QHP[JAS[PDNA=@[PNECCAN[PEIA( @AB=QHP[@UJ=IE?[PDNA=@[@A?=U[PEIA( @AB=QHP[PDNA=@[LNEKNEPU( @AB=QHP[NAMQAOP[MQAQA[HEIEP% w y lq^he_?qopkiPdna]`Lkkh$ejpejepe]hPdna]`?kqjp(ejpi]tPdna]`?kqjp(± opnejclkkhJ]ia(± ejpjasPdna]`Pneccan(ejp`uj]ie_Pdna]`@a_]uPeia(± Pdna]`Lneknepupdna]`Lneknepu(ejpnamqaopMqaqaHeiep% w D]j`ha9opkl?kilhapaArajp*D]j`ha7 eb$i]tPdna]`?kqjp8ejepe]hPdna]`?kqjp% w pdnksjas=ncqiajpAt_alpekj$I]teiqipdna]`_kqjpiqop^a:9 ejepe]hpdna]`_kqjp*(i]tPdna]`?kqjp%7 y eb$`uj]ie_Pdna]`@a_]uPeia89,% w pdnksjas=ncqiajpAt_alpekj$@uj]ie_pdna]``a_]upeia_]jjkp^a89,*( `uj]ie_Pdna]`@a_]uPeia%7 y eb$jasPdna]`Pneccan89,% w pdnksjas=ncqiajpAt_alpekj$Jaspdna]`pneccanpeia_]jjkp^a89,*( jasPdna]`Pneccan%7

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y pdeo*ejepe]hPdna]`?kqjp9ejepe]hPdna]`?kqjp7 pdeo*i]tPdna]`?kqjp9i]tPdna]`?kqjp7 pdeo*namqaopMqaqaHeiep9$namqaopMqaqaHeiep8,; @AB=QHP[NAMQAOP[MQAQA[HEIEP6namqaopMqaqaHeiep%7 pdeo*`a_]uPeia9`uj]ie_Pdna]`@a_]uPeia7 pdeo*jasPdna]`Pneccan9jasPeiaOl]j$± PeiaOl]j*Pe_goLanIehheoa_kj`&jasPdna]`Pneccan%7 pdeo*pdna]`Lneknepu9pdna]`Lneknepu7 pdeo*namqaopMqaqa9jasMqaqa$± namqaopMqaqaHeiep8,;0,526namqaopMqaqaHeiep%7  eb$lkkhJ]ia99jqhh% w pdnksjas=ncqiajpJqhhAt_alpekj$lkkhJ]ia(± Pdna]`lkkhj]ia_]jjkp^ajqhh%7 y ahoa w pdeo*pdna]`LkkhJ]ia9lkkhJ]ia7 y y ++PdaLneknepu"@uj]ie_Pdna]`@a_]ulnklanpeao]najkppdna]`o]ba ++]j`_]jkjhu^aoap^abknaOp]npeo_]hha`* lq^he_Pdna]`LneknepuLneknepu w capwnapqnj$pdna]`Lneknepu%7y  oap w eb$d]o>aajOp]npa`% w pdnksjasEjr]he`Klan]pekjAt_alpekj$?]jjkp]`fqoppdna]`± lneknepu]bpanlkkhd]o^aajop]npa`*%7 y pdna]`Lneknepu9r]hqa7 y y lq^he_ejp@uj]ie_Pdna]`@a_]u w capwnapqnj$`a_]uPeia%7y  oap w eb$d]o>aajOp]npa`% w pdnksjasEjr]he`Klan]pekjAt_alpekj$?]jjkp]`fqop`uj]ie_± pdna]``a_]upeia]bpanlkkhd]o^aajop]npa`*%7 y eb$r]hqa89,% w pdnksjas=ncqiajpAt_alpekj$@uj]ie_pdna]``a_]upeia± _]jjkp^a89,*(r]hqa%7 y

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`a_]uPeia9r]hqa7 y y lq^he_ejpJasPdna]`Pneccan w capwnapqnj$$ejp%jasPdna]`Pneccan*Pkp]hIehheoa_kj`o%7y  oap w eb$r]hqa89,% w pdnksjas=ncqiajpAt_alpekj$Jaspdna]`pneccanpeia_]jjkp± ^a89,*(r]hqa%7 y hk_g$pdeo% w jasPdna]`Pneccan9jasPeiaOl]j$± PeiaOl]j*Pe_goLanIehheoa_kj`&r]hqa%7 y y y lq^he_ejpNamqaopMqaqaHeiep w capwnapqnj$namqaopMqaqaHeiep%7y oapwnamqaopMqaqaHeiep9$r]hqa8,;@AB=QHP[NAMQAOP[MQAQA[HEIEP6r]hqa%7y y lq^he_ejp=r]eh]^haPdna]`o w capwnapqnj$i]tPdna]`?kqjp)_qnnajpPdna]`?kqjp%7y y lq^he_ejpI]tPdna]`o w capwnapqnj$i]tPdna]`?kqjp%7y oap w eb$r]hqa8ejepe]hPdna]`?kqjp% w pdnksjas=ncqiajpAt_alpekj$I]teiqipdna]`_kqjpiqop± ^a:9ejepe]hpdna]`_kqjp*(I]tPdna]`o%7 y i]tPdna]`?kqjp9r]hqa7 y y lq^he_^kkhEoOp]npa` w capwnapqnj$d]o>aajOp]npa`%7y y lq^he_^kkhLnklkc]paPdna]`Lnej_el]h w

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C H A P T E R 2 N W O R K E R A N D T H R E A D S

"EFORELOOKINGINTOTHEIMPLEMENTATIONDETAILSOFTHEUSAGESCENARIO ITISHELPFULTOUNDERSTAND how it works: ?qopkiPdna]`Lkkhpl-9jas?qopkiPdna]`Lkkh$.(2(Lkkh-%7 pl-*Lneknepu9Ouopai*Pdna]`ejc*Pdna]`Lneknepu*>ahksJkni]h7 pl-*JasPdna]`Pneccan90,,7 pl-*@uj]ie_Pdna]`@a_]u91,,,7 pl-*Op]np$%7 This starts a new thread pool using two initial threads and defines a maximum of six with low priority. The decay time is five seconds for testing purposes—the default is five minutes. The new THREADTRIGGERISSETTOMILLISECONDS The code used to test the thread pool requires an interface and a delegate, as defined in ,ISTING  Listing 2-15. Delegates and Base Interface for the Thread Pool lq^he_`ahac]parke`SkngNamqaop@ahac]pa$k^fa_pop]pa(± @]paPeianamqaopAjmqaqaPeia%7 lq^he_`ahac]parke`Pdna]`Lkkh@ahac]pa$%7 nacekjESkngNamqaopejpanb]_a lq^he_ejpanb]_aESkngNamqaop w ^kkh?]j_ah$%7 y aj`nacekj Once the pool is up and running, you can issue requests to get threads out of it. Doing so REQUIRESACALLBACKTHATSRESPONSIBLETOHANDLETHEWORKLOAD SkngNamqaop@ahac]pa_^-9jasSkngNamqaop@ahac]pa$?]hh^]_gKja%7 opnejc]nc97 Then a request internally starts the thread, using the callback to handle the worker method: pl-*LkopNamqaop$_^-(]nc%7 Once the threads are no longer required, the pool can be stopped: pl-*Opkl=j`S]ep$%7 This method call assures that the currently running threads can properly end its work before THETHREADPOOLISGOINGDOWNSEE,ISTING   Listing 2-16. The ThreadInfo Class That Provides the Thread-Specific HttpContext ejpanj]h_h]ooPdna]`Ejbk w lq^he_op]pe_Pdna]`Ejbk?]lpqna$^kkhlnklkc]paPdna]`Lnej_el]h(± ^kkhlnklkc]pa?]hh?kjpatp(± ^kkhlnklkc]paDppl?kjpatp(± ^kkhlnklkc]pa?=OI]ngano% w napqnjjasPdna]`Ejbk$lnklkc]paPdna]`Lnej_el]h(lnklkc]pa?]hh?kjpatp(± lnklkc]paDppl?kjpatp(lnklkc]pa?=OI]ngano%7 y lq^he_op]pe_Pdna]`EjbkEilanokj]pa$Pdna]`Ejbkpe%

97

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C H APT ER 2 N WO R K ER A ND THR EA DS

w eb$pe99jqhh%pdnksjas=ncqiajpJqhhAt_alpekj$pe%7 Pdna]`EjbklnarEjbk9?]lpqna$pnqa(pnqa(pnqa(pnqa%7 Naopkna$pe%7 napqnj$lnarEjbk%7 y lq^he_op]pe_rke`Naopkna$Pdna]`Ejbkpe% w eb$pe99jqhh%pdnksjas=ncqiajpJqhhAt_alpekj$pe%7 ++Naopkna_]hh_kjpatp* eb$ieOapHkce_]h?]hh?kjpatp9jqhh% w ieOapHkce_]h?]hh?kjpatp*Ejrkga$Pdna]`*?qnnajpPdna]`(± jask^fa_pWYwpe*_]hh?kjpatpy%7 y ++NaopknaDppl?kjpatpsepdpdaikn]hamqer]hajpkb ++Dppl?kjpatp*?qnnajp9pe*dppl?kjpatp7 ?]hh?kjpatp*Oap@]p]$Dppl?kjpatpOhkpJ]ia(pe*dppl?kjpatp%7 ++Naopknapdna]`e`ajpepu*Ep#oeilknp]jppd]ppdeo^a`kja]bpan ++naopknejc_]hh_kjpatp]^kra(oej_anaopknejc_]hh_kjpatp]hok ++kransnepaopda_qnnajppdna]`lnej_el]hoappejc*Eb ++lnklkc]pa?]hh?kjpatp ++]j`lnklkc]paPdna]`Lnej_el]h]na^kpdpnqa(pdajpda ++bkhhksejceona`qj`]jp* ++Dksaran(oej_alnklkc]pejc_]hh_kjpatpnamqenaopdaqoa ++kbnabha_pekjpk_]lpqna+naopkna_]hh_kjpatp(Es]jp ++pd]p^ad]reknpk^aej`alaj`ajphu ++osep_d]^haokpd]pep_]j^a`eo]^ha`7sdehaopehh]hhksejc ++pdna]`lnej_el]hpk^alnklkc]pa`* ++Pdeo]hok_kranoqoejpdaarajppd]p_]hh_kjpatp ++lnkl]c]pekj_d]jcaookpd]pepjkhkjcanlnklkc]paopdna]`lnej_el]h* Pdna]`*?qnnajpLnej_el]h9pe*lnej_el]h7 y lner]paPdna]`Ejbk$^kkhlnklkc]paPdna]`Lnej_el]h(^kkhlnklkc]pa?]hh?kjpatp(± ^kkhlnklkc]paDppl?kjpatp(^kkhlnklkc]pa?=OI]ngano% w eb$lnklkc]paPdna]`Lnej_el]h% w lnej_el]h9Pdna]`*?qnnajpLnej_el]h7 y eb$lnklkc]paDppl?kjpatp% w dppl?kjpatp9Dppl?kjpatp*?qnnajp7 y eb$lnklkc]pa?]hh?kjpatp""$ieCapHkce_]h?]hh?kjpatp9jqhh%% w _]hh?kjpatp9$Hkce_]h?]hh?kjpatp%± ieCapHkce_]h?]hh?kjpatp*Ejrkga$Pdna]`*?qnnajpPdna]`(jqhh%7 _]hh?kjpatp9$Hkce_]h?]hh?kjpatp%_]hh?kjpatp*?hkja$%7

C H A P T E R 2 N W O R K E R A N D T H R E A D S

y y ELnej_el]hlnej_el]h7 Hkce_]h?]hh?kjpatp_]hh?kjpatp7 ++=hs]uojqhhqjpehCap+Oap?kilnaooa`Op]_g]naklaja`ql* ?kilnaooa`Op]_g_kilnaooa`Op]_g9jqhh7 Dppl?kjpatpdppl?kjpatp7 ++?]_da`pulaejbkni]pekj* _kjop>ej`ejcBh]co^bJkjLq^he_Ejop]j_a9>ej`ejcBh]co*Ejop]j_ax± >ej`ejcBh]co*JkjLq^he_7 _kjop>ej`ejcBh]co^bJkjLq^he_Op]pe_9>ej`ejcBh]co*Op]pe_x± >ej`ejcBh]co*JkjLq^he_7 op]pe_Iapdk`EjbkieCapHkce_]h?]hh?kjpatp9± pulakb$Pdna]`%*CapIapdk`$CapHkce_]h?]hh?kjpatp(^bJkjLq^he_Ejop]j_a%7 op]pe_Iapdk`EjbkieOapHkce_]h?]hh?kjpatp9± pulakb$Pdna]`%*CapIapdk`$OapHkce_]h?]hh?kjpatp(^bJkjLq^he_Ejop]j_a%7 op]pe_opnejcDppl?kjpatpOhkpJ]ia7 op]pe_Pdna]`Ejbk$% w ++Hkkgqlpdar]hqakbDppl?kjpatp*?]hh?kjpatpOhkpJ]ia$ebepateopo% ++pkoaasd]ppdaj]iakbpda_]hh_kjpatpohkpeo ++sdanaDppl?kjpatp*?qnnajp ++eoop]oda`*=o]b]hh^]_g(ebpdeobeah`eoj#plnaoajp]juikna(fqop ++pnubknpdaknecej]hDppl?kjpatpohkpj]ia* Beah`Ejbkbe9pulakb$Dppl?kjpatp%*CapBeah`$?]hh?kjpatpOhkpJ]ia(± ^bJkjLq^he_Op]pe_%7 eb$be9jqhh% w Dppl?kjpatpOhkpJ]ia9$opnejc%be*CapR]hqa$jqhh%7 y ahoa w Dppl?kjpatpOhkpJ]ia9Dppl?kjpatp7 y y y The Pdna]`Ejbk class handles logical information regarding the current thread. This includes the Dppl?kjpatp object of current request. The idea is that several parallel running threads handle different contexts and need to restore the one currently being executed. The data are held in the Hkce_]h?]hh?kjpatpCLASSTHATHOLDSASETOFSERIALIZABLEPROPERTIESSEE,ISTING   Listing 2-17. The ThreadWrapper Class That Wraps the Actual Thread ejpanj]h_h]ooPdna]`Sn]llan w lner]pa?qopkiPdna]`Lkkhlkkh7 lner]pa^kkheoLani]jajp7 lner]paPdna]`Lneknepulneknepu7 lner]paopnejcj]ia7

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C H APT ER 2 N WO R K ER A ND THR EA DS

lq^he_Pdna]`Sn]llan$?qopkiPdna]`Lkkhlkkh(^kkheoLani]jajp(± Pdna]`Lneknepulneknepu(opnejcj]ia% w pdeo*lkkh9lkkh7 pdeo*eoLani]jajp9eoLani]jajp7 pdeo*lneknepu9lneknepu7 pdeo*j]ia9j]ia7 hk_g$lkkh% w ++Ql`]papdapkp]hkbpdna]`oejpdalkkh* lkkh*?qnnajpPdna]`?kqjp''7 y y lq^he_rke`Op]np$% w Pdna]`p9jasPdna]`$jasPdna]`Op]np$Pdna]`Lnk_%%7 p*=l]npiajpOp]pa9=l]npiajpOp]pa*IP=7 p*J]ia9j]ia7 p*Lneknepu9lneknepu7 p*Eo>]_gcnkqj`9lkkh*Qoa>]_gcnkqj`Pdna]`o7 p*Op]np$%7 y rke`Pdna]`Lnk_$% w ^kkh`kja9b]hoa7 sdeha$`kja% w SkngNamqaopsn9jqhh7 Pdna]`Sn]llanjasPdna]`9jqhh7 hk_g$lkkh% w ++=ohkjc]opdanamqaopmqaqaeoailpu]j`]odqp`ksjd]oj#p ++^aajejepe]pa`(s]epbkn]jasskngnamqaoppk]nnera* ^kkhpeia`Kqp9b]hoa7 sdeha$lkkh*OpklEjLnkcnaoo""peia`Kqp""± $lkkh*NamqaopMqaqa*?kqjp99,%% w eb$Ikjepkn*S]ep$lkkh(± $eoLani]jajp;Peiakqp*Ejbejepa6lkkh*@a_]uPeia%%% w ++Peia`kqps]epejcbknokiapdejcpk`k* ++Kjhu`uj]ie_]hhu_na]pa` ++pdna]`osehhcapdana(ok^]ehkqp* peia`Kqp9pnqa7 y y ++Saatepa`pdahkkl]^kra^a_]qoakjakbpda ++bkhhksejc_kj`epekjos]oiap6 ++)Pdna]`Lkkh*Opkls]o_]hha`pkejepe]pa]odqp`ksj* ++)=`uj]ie_pdna]`peia`kqps]epejcbkn]skngnamqaop ++)Pdana]naepaioejpdaskngmqaqapklnk_aoo* ++Ebsaatepa`pdahkkl^a_]qoapdana#oskngpk^a`kja(]

C H A P T E R 2 N W O R K E R A N D T H R E A D S

++odqp`ksjd]oj#p^aajejepe]pa`(]j`epeoj#p]`uj]ie_pdna]` ++pd]ppeia`kqp(lqhhpdanamqaopkbbpdamqaqa]j`lnal]napk ++lnk_aooep* eb$lkkh*OpklEjLnkcnaoo""peia`Kqp""± $lkkh*NamqaopMqaqa*?kqjp:,%% w sn9$SkngNamqaop%lkkh*NamqaopMqaqa*@amqaqa$%7 @a^qc*=ooanp$sn9jqhh%7 ++?da_gpkoaaebpdeoskngnamqaoph]jcqeoda`ejpdamqaqa ++ranuhkjc*Ebeps]oejpdamqaqa:9pdajaspdna]` ++pneccanpeia(]j`ebsad]raj#pna]_da`pdai]tpdna]` ++_kqjp_]l(]``]jaspdna]`pkpdalkkh* ++Ebpda`a_eoekjeoi]`a(_na]papdajaspdna]`k^fa_p ++$ql`]pejcpda_qnnajpkbpdna]`oejpdalkkh%( ++^qp`abanop]npejcpdajas ++pdna]`qjpehpdahk_geonaha]oa`* PeiaOl]jnamqaopPeiaEjM9@]paPeia*Jks*Oq^pn]_p$sn*skngejcPeia%7 eb$$namqaopPeiaEjM:9lkkh*JasPdna]`PneccanPeiaOl]j%""± $lkkh*?qnnajpPdna]`?kqjp8lkkh*I]tPdna]`?kqjp%% w jasPdna]`9± jasPdna]`Sn]llan$lkkh(b]hoa(lneknepu(± opnejc*Bkni]p$w,y$`uj]ie_%(± lkkh*Pdna]`LkkhJ]ia%%7 ++Oej_apda_qnnajpnamqaopsafqop`amqaqa`eoop]ha( ++aranupdejcahoa^adej`epejpdamqaqaeo]hokop]ha* ++Oknaoappdapeiaop]ilokbpdanai]ejejclaj`ejcskng ++namqaopookpd]psa`kj#pop]np_na]pejcpdna]`o ++bknaranuoq^oamqajpnamqaop* lkkh*NaoapSkngNamqaopPeiao$%7 y y ahoa w ++Odkqh`kjhucapdanaebpdeoeo]`uj]ie_pdna]`pd]p ++peia`kqps]epejcbkn]skngnamqaop(knebpdalkkh ++eoodqppejc`ksj* lkkh*?qnnajpPdna]`?kqjp))7 eb$lkkh*?qnnajpPdna]`?kqjp99,% w ++H]opkjakqppqnjokbbpdahecdpo* lkkh*KjOpklla`$%7 lkkh*Opkl?kilhapaArajp*Oap$%7 y `kja9pnqa7 y y++hk_g ++Jkhkjcandkh`ejclkkhhk_gdana*** eb$`kja""$sn9jqhh%% w

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C H APT ER 2 N WO R K ER A ND THR EA DS

++?da_gpkoaaebpdeonamqaopd]o^aaj_]j_ahha`sdeha ++opq_gejpdaskngmqaqa* ++Ebpdaskngnamqaops]olaj`ejc(i]ngeplnk_aooa`]j` ++lnk_aa`pkd]j`ha*Kpdanseoa(pdanamqaopiqopd]ra^aaj ++_]j_ahha`^abknasalhq_ga`epkbbpdanamqaopmqaqa* eb$Ejpanhk_ga`*?kil]naAt_d]jca$nabsn*op]pa(± SkngNamqaop*LNK?AOOA@(± SkngNamqaop*LAJ@EJC%9SkngNamqaop*LAJ@EJC% w ++Namqaops]o_]j_ahha`^abknasa_kqh`capdana* ++>]ehkqp* _kjpejqa7 y eb$jasPdna]`9jqhh% w jasPdna]`*Op]np$%7 y ++@eol]p_dpdaskngnamqaop* Pdna]`Ejbkknecej]hPdna]`Ejbk9jqhh7 pnu w ++Eilanokj]pa$]oiq_d]olkooe^ha%sd]psagjks]^kqp ++pdapdna]`pd]peooqa`pdaskngnamqaop* knecej]hPdna]`Ejbk9Pdna]`Ejbk*Eilanokj]pa$sn*pdna]`Ejbk%7 SkngNamqaop@ahac]pap]ncapLnk_9sn*p]ncapLnk_]o± SkngNamqaop@ahac]pa7 eb$p]ncapLnk_9jqhh% w p]ncapLnk_$sn*lnk_=nc(sn*peiaOp]ilOp]npa`%7 y ahoa w sn*p]ncapLnk_*@uj]ie_Ejrkga$sn*lnk_=nco%7 y y _]p_d$At_alpekja% w y bej]hhu w ++Naopknakqnsknganpdna]`#oe`ajpepu* ++ Pdna]`Ejbk*Naopkna$knecej]hPdna]`Ejbk%7 y y y y y 7HILETHETHREADISTHERETODOTHEWORK ANOTHERPIECEINTHEPUZZLEISREQUIREDˆTHESkngNamqaop. This type contains the reference between the callback method that is handling the workload and the THREAD,ISTING  

C H A P T E R 2 N W O R K E R A N D T H R E A D S

Listing 2-18. The WorkRequest Class That Associates Request and Thread ejpanj]h_h]ooSkngNamqaop6ESkngNamqaop w ejpanj]h_kjopejpLAJ@EJC9,7 ejpanj]h_kjopejpLNK?AOOA@9-7 ejpanj]h_kjopejp?=J?AHHA@9.7 lq^he_SkngNamqaop$SkngNamqaop@ahac]pa_^(k^fa_p]nc( ^kkhlnklkc]paPdna]`Lnej_el]h(^kkhlnklkc]pa?]hh?kjpatp( ^kkhlnklkc]paDppl?kjpatp(^kkhlnklkc]pa?=OI]ngano% w p]ncapLnk_9_^7 lnk_=nc9]nc7 lnk_=nco9jqhh7 Ejepe]heva$lnklkc]paPdna]`Lnej_el]h(lnklkc]pa?]hh?kjpatp( lnklkc]paDppl?kjpatp(lnklkc]pa?=OI]ngano%7 y lq^he_SkngNamqaop$@ahac]pa_^(k^fa_pWY]nco( ^kkhlnklkc]paPdna]`Lnej_el]h(^kkhlnklkc]pa?]hh?kjpatp( ^kkhlnklkc]paDppl?kjpatp(^kkhlnklkc]pa?=OI]ngano% w p]ncapLnk_9_^7 lnk_=nc9jqhh7 lnk_=nco9]nco7 Ejepe]heva$lnklkc]paPdna]`Lnej_el]h(lnklkc]pa?]hh?kjpatp( lnklkc]paDppl?kjpatp(lnklkc]pa?=OI]ngano%7 y rke`Ejepe]heva$^kkhlnklkc]paPdna]`Lnej_el]h(^kkhlnklkc]pa?]hh?kjpatp( ^kkhlnklkc]paDppl?kjpatp(^kkhlnklkc]pa?=OI]ngano% w skngejcPeia9peiaOp]ilOp]npa`9@]paPeia*Jks7 pdna]`Ejbk9Pdna]`Ejbk*?]lpqna$lnklkc]paPdna]`Lnej_el]h(± lnklkc]pa?]hh?kjpatp(± lnklkc]paDppl?kjpatp(± lnklkc]pa?=OI]ngano%7 y lq^he_^kkh?]j_ah$% w ++Ebpdaskngnamqaops]olaj`ejc(i]ngep_]j_ahha`*Kpdanseoa( ++pdeoiapdk`s]o_]hha`pkkh]pa*Jkpapd]ppdeo_]hh_]j ++_]j_ah]jklan]pekjsepdkqp]jun]_a_kj`epekjo*>qpebpda ++naoqhpkbpdeopaop)]j`)oapej`e_]paopdanamqaopeoejpda ++lnk_aooa`op]pa(epiecdp]_pq]hhu^a]^kqppk^alnk_aooa`* napqnj$Ejpanhk_ga`*?kil]naAt_d]jca$nabop]pa(?=J?AHHA@(LAJ@EJC%± 99LAJ@EJC%7 y ++Bqj_pekjpk_]hh* ejpanj]h@ahac]pap]ncapLnk_7 ++Op]papkl]oopkbqj_pekj* ejpanj]hk^fa_plnk_=nc7 ++Qoa`sepd@ahac]pa*@uj]ie_Ejrkga*

103

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C H APT ER 2 N WO R K ER A ND THR EA DS

ejpanj]hk^fa_pWYlnk_=nco7 ++Peiaskngnamqaops]oknecej]hhuajmqaqa`$dah`_kjop]jp%* ejpanj]h@]paPeiapeiaOp]ilOp]npa`7 ++?qnnajppeiaop]ilqoa`bknpneccanejcjaspdna]`o$ikrejcp]ncap%* ejpanj]h@]paPeiaskngejcPeia7 ++Aranupdejcsagjks]^kqp]pdna]`* ejpanj]hPdna]`Ejbkpdna]`Ejbk7 ++Pdaop]pakbpdeol]npe_qh]nnamqaop* ejpanj]hejpop]pa9LAJ@EJC7 y The goal is the function that contains the worker code stored in p]ncapLnk_. The field lnk_=nco held the particular arguments. The field pdna]`Ejbk contains the associated information, especially the Dppl?kjpatp object. This all creates the necessary functions to have threads ready to be used any time and indepenDENTOFTHEINTERNALTHREADPOOL.OWTHATYOUHAVEACUSTOMTHREADPOOLIMPLEMENTATION ITSTIME to use it.

Using the Custom Thread Pool with ASP.NET’s Asynchronous Handler The following example is simply an extended version of the previous one. Instead of using single threads, however, and risk having too many of them, you can use the custom thread pool and set SOMELIMITATIONSSEE,ISTING   Listing 2-19. Using the Thread Pool 8))Beha6=ouj_Lkkh*]odt)): 8!<Sa^D]j`hanH]jcq]ca9? ?h]oo9=lnaoo*Pdna]`ejc*DpplLelaheja*=ouj_D]j`han!: j]iaol]_a=lnaoo*Pdna]`ejc*DpplLelaheja w  lq^he__h]oo=ouj_D]j`han6EDppl=ouj_D]j`han w op]pe_=lnaoo*Atpajoe^ehepu*Pdna]`ejc*?qopkiPdna]`Lkkh[pdna]`Lkkh7 op]pe_=ouj_D]j`han$% w [pdna]`Lkkh9± jas=lnaoo*Atpajoe^ehepu*Pdna]`ejc*?qopkiPdna]`Lkkh$.(.1(=ouj_Lkkh%7 [pdna]`Lkkh*Lnklkc]pa?]hh?kjpatp9pnqa7 [pdna]`Lkkh*Lnklkc]paPdna]`Lnej_el]h9pnqa7 [pdna]`Lkkh*Lnklkc]paDppl?kjpatp9pnqa7 [pdna]`Lkkh*Op]np$%7 y lq^he_rke`Lnk_aooNamqaop$Dppl?kjpatp_pt% w ++jkpqoa`(bknouj_kjhu y lq^he_^kkhEoNaqo]^ha w capwnapqnjb]hoa7y y

C H A P T E R 2 N W O R K E R A N D T H R E A D S

lq^he_E=ouj_Naoqhp>acejLnk_aooNamqaop$Dppl?kjpatp_pt(± =ouj_?]hh^]_g_^(k^fa_pk^f% w =ouj_NamqaopOp]panamOp]pa9± jas=ouj_NamqaopOp]pa$_pt(_^(k^f%7 [pdna]`Lkkh*LkopNamqaop$jasSkngNamqaop@ahac]pa$Lnk_aooNamqaop%(namOp]pa%7 napqnjnamOp]pa7 y lq^he_rke`Aj`Lnk_aooNamqaop$E=ouj_Naoqhp]n% w y rke`Lnk_aooNamqaop$k^fa_pop]pa(@]paPeianamqaopPeia% w =ouj_NamqaopOp]panamOp]pa9op]pa]o=ouj_NamqaopOp]pa7 ++P]gaokiapeiapk`kep Pdna]`*Ohaal$.,,,%7  namOp]pa*[_pt*Naolkjoa*Kqplqp*Snepa$± =ouj_Pdna]`Lkkh(w,y(± =ll@ki]ej*Cap?qnnajpPdna]`E`%7 ++pahh]ol*japukq]nabejeoda`lnk_aooejcpdeonamqaop namOp]pa*?kilhapaNamqaop$%7 y y y )NTHEORY THISTHREADPOOLWILLNOTRUNOUTOFTHREADSUNLESSITDOESNOTREACHTHELIMITOF  THREADSALLOWED(OWEVER THEREARESOMELIMITATIONS SUCHASAVAILABLEMEMORY #05POWER AND operating system restrictions. This is why the pool was designed, so that you can optionally specify limits. The previous code is a good platform for experimenting with threads and thread pools, and for monitoring the number of threads for your application. If you want to replace the internal thread pool, try out the custom pool toLEARNHOW!30.%4REQUESTSTHREADS, and find out where to improve performance.

Summary This chapter covered in-depth information about the internal request processing and how to tweak the worker process and the threading. You were given an idea of how the thread pool works and how TOEXTENDTHEBEHAVIOR5SINGASYNCHRONOUSPROCESSINGMIGHTINCREASEPERFORMANCEANDHANDLE HIGHWORKLOAD!CUSTOMTHREADPOOLWASINTRODUCEDTODEMONSTRATEHOWTOCHANGEINTERNALPARTS of the processing pipeline transparently. In anticipation of Chapter 3, you had a first look into asynchronous handlers and their usage.

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3

Modules and Handlers

I

n this chapter, you will look more closely at the extensibility of ASP.NET through the addition of custom modules and handlers. Handlers and modules are integrated into IIS so that your web applications can perform and scale well. In Chapter 2, you learned how to use asynchronous handlers to handle custom threads. Here, you’ll learn more about how ASP.NET can extend using handlers. This chapter includes:

s 7HATINTERNALMODULESAREFOR



s (OWTOCREATE ACTIVATE ANDDEBUGCUSTOMMODULES



s 4HEHANDLERSINCLUDEDIN!30.%4



s (OWTOEXTEND CUSTOMIZE ANDREPLACEHANDLERS



s 7RITINGYOUROWNHANDLERSWITHBOTHSYNCHRONOUSANDASYNCHRONOUSBEHAVIOR

Module, Handlers, and IIS ))37EB3ERVERFEATURESFITINTOONEOFTWOCATEGORIES

s -ODULES



s (ANDLERS

Similar to the ISAPI filterINPREVIOUS))3VERSIONS AMODULE participates in the processing of each request. Its role is to change or add content to the request. Examples of some out-of-the-box modules in IIS7 include authentication modules, compression modules, and logging modules. The names indicate the function of each module. A module is a .NET class that implements the Ouopai*Sa^*EDpplIk`qha interface and uses APIs in the Ouopai*Sa^ namespace to participate in one or more of ASP.NET’s request-processing stages. I explained the stages of this “pipeline” in Chapter 1. By contrast, a handler, similar to the ISAPI extensionINPREVIOUS))3VERSIONS ISRESPONSIBLEFOR handling requests and creating responses for specific content types. The main difference between modules and handlers is that handlers typically map to a particular request path or extension. They also support the processing of a specific resource to which that path or extension corresponds. (ANDLERSPROVIDEDWITH))3INCLUDE!30.%4SL]caD]j`hanB]_pknu, which processes .aspx pages, among others. This kind of a handler is a .NET class that implements the ASP.NET Ouopai*Sa^* EDpplD]j`han or Ouopai*Sa^*EDppl=ouj_D]j`han interface. It uses APIs in the Ouopai*Sa^ namespace to produce an HTTP response for the specific content it creates. 7HENDEVELOPINGAN))3FEATUREOR!30.%4EXTENSION YOULLNEEDTODECIDEWHETHERAMODule or a handler is appropriate. No common task requires both. If your feature is responsible for SERVINGREQUESTSTOASPECIFIC52,ORFILEEXTENSION LIKE&*ljc, then a handler is the right choice, as 107

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HANDLERSAREPRIMARILYFORSPECIFICTASKS!LTERNATIVELY IFYOUWANTTORESPONDTOSOMEORALLREQUESTS a module is appropriate. #REATINGIMAGESONTHEFLYCORRESPONDSTOASPECIFICFILETYPEˆUSEAHANDLERTOACHIEVETHIS Adding footers to all your pages from one location is a good idea—implement a module to do that.

Modules 4HISSECTIONEXPLAINSHOWTOCREATEINTERNALMODULESANDGIVESSOMEEXAMPLESTHATYOUCANUSEIN your own applications.

IIS7 Architecture ASP.NET isTIGHTLYINTEGRATEDWITH))3%VENTHOUGHITISPOSSIBLE to run ASP.NET with any host, thanks to its modular architecture, you should keep in mind that IIS is the best platform “by design.” %XTENDINGANDCUSTOMIZING!30.%4ISONLYPOSSIBLEWITHAGOODUNDERSTANDINGOF))3ANDITSPARTS -ICROSOFTCHANGEDLARGEPARTSOFTHEARCHITECTUREOF))3COMPAREDTOPREVIOUSVERSIONS/NEOF THEMAJORCHANGESWASTHEGREATLYENHANCEDEXTENSIBILITY)NSTEADOFAPOWERFULYETMONOLITHIC7EB 3ERVER ))3NOWHASA7EB3ERVERENGINETOWHICHYOUCANADDORREMOVECOMPONENTS4HESECOMponents are called modules. -ODULESBUILDTHEFEATURESOFFEREDBYTHE7EB3ERVER!LLMODULESHAVEONEPRIMARYTASKˆ PROCESSINGAREQUEST4HISCANBECOMECOMPLICATED HOWEVER ASAREQUESTISNOTJUSTACALLTOSTATIC RESOURCES#ONSIDERREQUESTSINVOLVINGTHEAUTHENTICATIONOFCLIENTCREDENTIALS COMPRESSIONAND decompression, or cache management. Assuming that IIS7 is the primary platform for running ASP.NET, any discussion about extensibility does not make sense without understanding what accompanies IIS7. IIS7 comes with two module types:

s .ATIVE-ODULES



s -ANAGED-ODULES

Native Modules .ATIVEMODULESPERFORMALLTHEBASICTASKSOFA7EB3ERVER(OWEVER NOTALLMODULESMANAGECOMMONREQUESTS)TDEPENDSONYOURINSTALLATIONANDCONFIGURATIONASTOWHETHERAMODULEISAVAILABLE and running. Inside IIS7 are:

s (440-ODULES



s 3ECURITY-ODULES



s #ONTENT-ODULES



s #OMPRESSION-ODULES



s #ACHING-ODULES



s ,OGGINGAND$IAGNOSING-ODULES



s )NTEGRATIONOF-ANAGED-ODULES

C H A P T E R 3 N M O D U LE S A N D H A N D LE R S

You can find all modules—apart from those whose full path follow—in the following directory: !Sej@en!XOuopai/.XEjapOnr As shown in Table 3-1, the HTTP modules perform tasks specific to Hypertext Transfer Protocol. Table 3-1. HTTP Modules Module Name

DLL

Description

?qopkiAnnknIk`qha

Custerr.dll

Its purpose is to send default or configured HTTP error messages when the response contains an error status.

DpplNa`ena_pekjIk`qha

2EDIRECTDLL

-ODULESUPPORTSCONFIGURABLEREDIRECTIONFOR HTTP requests.

Lnkpk_khOqllknpIk`qha 

Protsup.dll

This module executes protocol-related actions, such as setting response headers and redirecting headers.

SecurityISESSENTIALFORA7EB3ERVER ASSHOWNBYTHENUMBEROFMODULESIN4ABLE  Table 3-2. Security Modules

Module Name

DLL

Description

=jkjuikqo=qpdajpe_]pekjIk`qha

Authanon.dll

Accomplishes anonymous authentication in case other authentication methods fail.

>]oe_=qpdajpe_]pekjIk`qha

Authbas.dll

Performs Basic authentication.

?anpebe_]paI]llejc=qpdajpe_]pekjIk`qha

Authcert.dll

0ERFORMS#ERTIFICATE-APPING AUTHENTICATIONUSING!CTIVE $IRECTORY

@ecaop=qpdajpe_]pekjIk`qha

Authmd5.dll

0ERFORMS$IGESTAUTHENTICATION

EEO?anpebe_]paI]llejc=qpdajpe_]pekjIk`qha

Authmap.dll

0ERFORMS#ERTIFICATE-APPING authentication using IIS certificate configuration.

NamqaopBehpanejcIk`qha

-ODRQFLTDLL

Performs tasks such as conFIGURINGALLOWEDVERBSANDFILE extensions, setting limits, and scanning for bad character seQUENCESBYSCANNINGTHE52,

Qnh=qpdknev]pekjIk`qha

5RLAUTHZDLL

%XECUTES52,AUTHORIZATION

Sej`kso=qpdajpe_]pekjIk`qha

Authsspi.dll

0ERFORMS.4,-INTEGRATED authentication.

ElNaopne_pekjIk`qha 

iprestr.dll

4HEPURPOSEISTORESTRICT)0V addresses listed in the IpSecurity list.

/NCETHEREQUESTISACCEPTEDANDAUTHORIZED THEREQUESTEDRESOURCESAREHANDLED3EVERAL modules perform these specific tasks. Table 3-3 shows the modules that handle content directly, like static files.

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Table 3-3. Content Modules

Module Name

DLL

Description

?ceIk`qha

Cgi.dll

Executes Common Gateway Interface (CGI) processes to build response output.

@ab]qhp@k_qiajpIk`qha

$EFDOCDLL

Attempts to return a default document for requests made to the parent directory.

@ena_pknuHeopejcIk`qha

dirlist.dll

,ISTSTHECONTENTSOFADIRECTORYANDBUILDSA(4-, response of the listing.

Eo]leIk`qha

Isapi.dll

4HISMODULESHOSTSOTHER)3!0)EXTENSION$,,S

Eo]leBehpanIk`qha

Filter.dll

4HISMODULESUPPORTS)3!0)FILTER$,,S

OanranOe`aEj_hq`aIk`qha

Iis_ssi.dll

4HISMODULEISRESPONSIBLEFORSERVER SIDEINCLUDE CODE AFORMERMODULARIZATIONTECHNIQUE

Op]pe_BehaIk`qha

Static.dll

4HISMODULESERVESSTATICFILES SUCHASIMAGES

B]op?ceIk`qha 

iisfcgi.dll

3UPPORTS&AST#') WHICHPROVIDESAHIGH PERFORMANCE ALTERNATIVETO#')5SEDTOSUPPORTWEBDEVELOPMENT ENVIRONMENTSLIKE0(0

CompressionISACOMMONWAYTOSAVEBANDWIDTHANDTRANSFERLARGEFILESMOREEFFICIENTLYSEE 4ABLE   Table 3-4. Compression Modules

Module Name

DLL

Description

@uj]ie_?kilnaooekjIk`qha

Compdyn.dll

5SEDTOCOMPRESSRESPONSESUSINGgzip compression transfer coding on the fly

Op]pe_?kilnaooekjIk`qha

Compstat.dll

Performs the pre-compression of static content

CachingISANOTHERWAYTOIMPROVEPERFORMANCE3EVERALMODULESSTOREFILESSOTHATTHEDELIVERY process is either accelerated or eliminated altogether (see Table 3-5). Table 3-5. Caching Modules

Module Name

DLL

Description

Beha?]_daIk`qha

Cachfile.dll

0ROVIDESUSERMODECACHINGFORFILESANDFILEHANDLES

DPPL?]_daIk`qha

Cachhttp.dll

0ROVIDESKERNELMODEANDUSERMODECACHINGIN(440SYS DRIVER

Pkgaj?]_daIk`qha

Cachtokn.dll

0ROVIDESUSERMODECACHINGOFUSERNAMEANDTOKENPAIRSFOR MODULESTHATUSE7INDOWSUSERPRINCIPALS

Qne?]_daIk`qha

Cachuri.dll

0ROVIDESUSERMODECACHINGOF52,INFORMATION

C H A P T E R 3 N M O D U LE S A N D H A N D LE R S

+NOWINGWHATISHAPPENINGISESSENTIALFOR7EB3ERVERADMINISTRATORS4HEREARESEVERAL STEPSFROMTHECODEONYOURSERVERˆWHEREYOUPROBABLYHAVEDEBUGCAPABILITIESˆTOTHEBROWSER WHEREYOUMIGHTMISSSEEINGTHEDESIREDOUTPUT%VENPRODUCTIONSYSTEMSDONOTALWAYSBEHAVEAS expected. Table 3-6 shows logging and diagnostic modules, which help you understand the internal processing of requests and responses. Table 3-6. Logging and Diagnostic Modules

Module Name

DLL

Description

?qopkiHkccejcIk`qha

,OGCUSTDLL

,OADSADDITIONALCUSTOMLOGGINGMODULES

B]eha`NamqaopoPn]_ejcIk`qha

Iisfreb.dll

4HISMODULESUPPORTSTHEh&AILED2EQUEST4RACINGv feature.

DpplHkccejcIk`qha

,OGHTTPDLL

This module passes information and processing STATUSTOTHE(440SYSDRIVERFORLOGGINGPURPOSES

NamqaopIkjepknIk`qha

Iisreqs.dll

This module tracks requests currently executing in worker processes and reports information using the 2UNTIME3TATUSAND#ONTROL!PPLICATION0ROGRAMMING)NTERFACE23#! 

Pn]_ejcIk`qha

Iisetw.dll

2EPORTSEVENTSTO-ICROSOFT%VENT4RACINGFOR 7INDOWS%47 

Finally, you need an interface to the managed world. In Chapter 1, you saw how modules interacted. Table 3-7 shows which modules areINVOLVEDINTHISINTERACTION Table 3-7. Integration of Managed Modules

Module Name

DLL/Assembly

Description

I]j]ca`Ajceja

-ICROSOFT.%4<&RAMEWORK< V<WEBENGINEDLL

0ROVIDESINTEGRATIONOFMANaged code modules in the IIS request-processing pipeline. The VERSIONNUMBERMIGHTCHANGE

?kjbecqn]pekjR]he`]pekjIk`qha VALIDCFGDLL    

Validates configuration issues, such as if an application is running in Integrated mode but has handlers or modules declared in the system.web section of web. config file.

Managed Modules 7HILEEXTENDING))3VIANATIVEMODULESISONEMETHODOFWRITINGHIGH PERFORMANCEAPPLICATIONS for most projects, this is not necessary or desirable. Extending ASP.NET using managed modules HASSIGNIFICANTADVANTAGESINDEVELOPMENTTIMEANDRELIABILITY))3INCLUDESSEVERALBUILT IN MANAGEDMODULES WHICHSHOWTHATITISPOSSIBLETOWRITELOW LEVELINFRASTRUCTURECOMPONENTSIN managed code.

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You can find the definition of security modules in the Ouopai*Sa^*Oa_qnepu namespace (see Table 3-8). Table 3-8. Managed Code Security Modules Shipped with IIS7

Module Name

Class

Description

AnonymousIdentification

=jkjuikqoE`ajpebe_]pekjIk`qha

-ANAGESANONYMOUSIDENTIFIERS which are used by features to support anonymous identification such as the ASP.NET profile.

$EFAULT!UTHENTICATION

@ab]qhp=qpdajpe_]pekjIk`qha

Ensures that a default authentication object is present in the context.

&ILE!UTHORIZATION

Beha=qpdknev]pekjIk`qha

Verifies that a user has permission to access the requested file based on file security.

FormsAuthentication

Bknio=qpdajpe_]pekjIk`qha

Supports authentication using the Forms authentication technique.

2OLE-ANAGER

NkhaI]j]canIk`qha

-ANAGESA2OLE0RINCIPALINSTANCE for the current user and therefore the role management. This is EXTENSIBLETHROUGHPROVIDERS

5RL!UTHORIZATION

Qnh=qpdknev]pekjIk`qha

$ETERMINESWHETHERTHECURRENT user is permitted to access the reQUESTED52, BASEDONTHEUSERS name or his or her membership of a suitable role.

7INDOWS!UTHENTICATION

Sej`kso=qpdajpe_]pekjIk`qha 

Supports the identity of a user WHEN7INDOWSAUTHENTICATIONIS enabled for the application.

Table 3-9 shows some more modules for particular usage. The definition of the cache module is stored in Ouopai*Sa^*?]_dejc. This module is declared as ejpanj]h and is not accessible by user code. The other ones are declared lq^he_. The module for profile handling is in the Ouopai*Sa^* Lnkbeha namespace. For session handling modules, look into the Ouopai*Sa^*OaooekjOp]pa NAMESPACE4HEMODULESFOR52,HANDLINGARESTOREDINTHEROOTNAMESPACEOuopai*Sa^. Table 3-9. Managed Code Modules Shipped with IIS7

Module Name

Class

Description

/UTPUT#ACHE

Kqplqp?]_daIk`qha

This module supports output caching.

Profile

LnkbehaIk`qha

-ANAGESUSERPROFILESBYUSING!30.%4PROFILES WHICHSTOREANDRETRIEVEUSERSETTINGSINADATA source such as a database. This is extensible THROUGHPROVIDERS

Session

OaooekjOp]paIk`qha

Supports the maintenance of the session state, which enables the storage of data specific to a sinGLECLIENTONTHESERVER4HISISEXTENSIBLETHROUGH PROVIDERS

5RL-APPINGS-ODULE

QnhI]llejcoIk`qha

3UPPORTSTHEMAPPINGOFAREAL52,TOAMORE USER FRIENDLYOREVENASEARCH ENGINEFRIENDLY52,

C H A P T E R 3 N M O D U LE S A N D H A N D LE R S

'IVENTHISLISTOFMODULES YOUMIGHTFEELTHATTHEREISNONEEDTOWRITECUSTOMMODULESTOPERFORMSTANDARDTASKS4HISISTRUETHEDEVELOPERSOF!30.%4AND))3HAVEDELIVEREDEVERYTHINGYOU NEEDFORCOMMONINFRASTRUCTUREWORK(OWEVER IFYOUDLIKETOPROGRAMANAPPLICATION SPECIFIC task, writing your own module is an excellent way to extend ASP.NET and add sophisticated features of your choice.

The IIS7 Managed Module Starter Kit -ICROSOFTPROVIDES a starter kit to make it easy to write your first module for the new IIS7 managed !0)4HIS6ISUAL3TUDIO#ONTENT)NSTALLERCONTAINSAPROJECTTEMPLATEFORBUILDING))3-ODULES using the .NET Framework.

Get the Starter Kit The Starter Kit isAVAILABLEATNOCOSTFROM-ICROSOFTATTHEsss*eeo*jap7EBSITEdppl6++sss*eeo* jap+`ksjhk]`o+`ab]qhp*]olt;p]^e`9/0"e9-/,."c92. #LICKON$OWNLOAD SAVETHEFILE ANDUNZIPTOACURRENTFOLDER4HEKITISA6ISUAL3TUDIOTEMPLATEINSTALLER PROVIDED as a .roe file.

Benefits of Module Development Kit Since IIS7 supportsDEVELOPMENTUSINGMANAGEDCODE ITMEANSYOUCANPROGRAM(440REQUEST PROCESSINGINMANAGEDCODE4HEENTIREEVENTSTRUCTUREOF))3 WRITTENINNATIVE!0)## ISALSO AVAILABLETOMANAGEDCODEDEVELOPERS&IGURE SHOWSTHESTARTSCREENOFTHEINSTALLATIONWIZARD

Figure 3-1. Installing the template

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NNote

Using the Starter Kit simplifies the first steps. However, you don’t need it to run the samples provided in this chapter.

/NCEYOUINSTALLTHETEMPLATE YOUCANADDNEWMODULESBYUSINGTHERIGHTITEMFORYOURPROJECT !DDITIONALLY YOUCANUSETHEh))3-ANAGED-ODULEvPROJECTTEMPLATETOCREATEANEWPROJECTWITH APREDEFINEDMODULECLASSALREADYTHERE4HEPROJECTTEMPLATEPROVIDESACOMPREHENSIVEINSTRUCtion, too (see Figure 3-2).

Figure 3-2. Adding a new module code item to a current project 4HISITEMCREATESACLASSSKELETON ASSHOWNIN,ISTING  Listing 3-1. Skeleton of a Module Class qoejcOuopai7 qoejcOuopai*Sa^7 j]iaol]_a=lnaoo*Atpajoe^ehepu*DpplIk`qhao w lq^he__h]ooIuIk`qha6EDpplIk`qha w +++8oqii]nu: +++Ukqsehhjaa`pk_kjbecqnapdeoik`qhaejpdasa^*_kjbecbeha +++]j`naceopanepsepdEEO^abkna^aejc]^hapkqoaep* +++Bkniknaejbkni]pekj +++oaapdabkhhksejchejg6dppl6++ck*ie_nkokbp*_ki+;hejge`94-,-,,3 +++8+oqii]nu: nacekjEDpplIk`qhaIai^ano

C H A P T E R 3 N M O D U LE S A N D H A N D LE R S

++@eolkoaokbpdanaokqn_ao$kpdanpd]jiaiknu%qoa`^updaik`qha* lq^he_rke`@eolkoa$% w ++_ha]j)ql_k`adana* y ++Ejepe]hevaopdaik`qha(]j`naceopanobkn]llhe_]pekjarajpo* lq^he_rke`Ejep$Dppl=llhe_]pekj]llhe_]pekj% w ++Sd]pbkhhksoeo]jat]ilhakbdksukq_]jd]j`haHkcNamqaop ++arajp]j`lnkre`a ++_qopkihkccejceilhaiajp]pekjbknep ]llhe_]pekj*HkcNamqaop'9jasArajpD]j`han$KjHkcNamqaop%7 y aj`nacekj lq^he_rke`KjHkcNamqaop$K^fa_pokqn_a(Arajp=ncoa% w ++_qopkihkccejchkce__]jckdana y y y For the sake of clarity and space, I will not repeat this part of the module code in the following sections when examining theVARIOUSEXAMPLES

Building a Module !SREQUESTSMOVETHROUGHTHEPIPELINE ANUMBEROFEVENTSFIRE on the Dppl=llhe_]pekj object. !SYOUVESEENALREADY THESEEVENTSPUBLISHASEVENTMETHODSINGlobal.asax. This approach is application-specific, but not always ideal. If you want to build generic Dppl=llhe_]pekjEVENTHOOKS THATCANPLUGINTOANY7EBAPPLICATION YOUCANUSEDpplIk`qhao. These are reusable and require an entry in web.config instead of application-specific code.

Define the Modules -ODULESALLOWYOUTOHOOKEVENTSFORANYREQUESTTHATPASSESTHROUGHTHE!30.%4Dppl=llhe_]pekj object. These modules are stored as classes in external assemblies configured in web.config, which causes them to load when the application starts. By implementing specific interfaces and methods, the module hooks up to the Dppl=llhe_]pekjEVENTCHAIN-ULTIPLEDpplIk`qhao can hook the same EVENT4HEIRORDERISDETERMINEDBYAPPEARANCEINweb.config,ISTING SHOWSAHANDLERDEFINITION in web.config. Listing 3-2. Register a Module in web.config 8_kjbecqn]pekj: 8ouopai*sa^: 8dpplIk`qhao: 8]``j]ia9IuIk`qha± pula9=lnaoo*Atpajoe^ehepu*DpplIk`qhao*Ik`qhao(IuIk`qha+: 8+dpplIk`qhao: 8+ouopai*sa^: 8+_kjbecqn]pekj:

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.OTETHATYOUNEEDTOSPECIFYBOTHAFULLTYPENAMEANDANASSEMBLYNAMEWITHOUTTHE$,, extension. -ODULESALLOWYOUTOOBSERVEEACHINCOMINGREQUESTANDPERFORMANACTIONBASEDONTHE EVENTSTHATFIRE-ODULESAREEXCELLENTFORMODIFYINGAREQUESTORRESPONDINGTOPARTICULARCONTENTIN ORDERTOPROVIDECUSTOMAUTHENTICATIONORPRE ORPOST PROCESSINGTOEACHREQUESTTHATARRIVES -ANYOF!30.%4SFEATURES SUCHASTHE!UTHENTICATIONAND3ESSIONENGINES AREIMPLEMENTED AS(440-ODULES7HILEDpplIk`qhao might feel similar to ISAPI FiltersINTHATTHEYEXAMINEEVERY REQUESTTHATARRIVESTHROUGHAN!30.%4APPLICATION INREALITYTHEYARELIMITEDTOSCRUTINIZING REQUESTSMAPPEDTOASINGLESPECIFIC!30.%4APPLICATIONORVIRTUALDIRECTORY Therefore, you can inspect all *]olt pages or any other custom extensions that map to this APPLICATION(OWEVER YOUCANNOTLOOKATSTANDARDHTMLORIMAGEFILESUNLESSYOUEXPLICITLYMAPTHE extension to the ASP.NET ISAPI.dll.

Example—Write a Simple Authentication Module This first example shows how to intercept the authentication procedure of the request pipeline. It also demonstrates how to add your own authentication module to handle tasks independently of the existing code. )MPLEMENTINGAN(440-ODULEISVERYEASY)MPLEMENTTHEEDpplIk`qha interface, which contains two methods: Ejep and @eolkoa.

NNote The Starter Kit item additionally creates a HkcNamqaop handler, if you add the module using the ASP.NET module item. If you use the IIS7 Managed Module project with the first module item predefined, the LnaNamqaopD]j`hanAta_qpa event is already hooked. You can safely remove these handlers and their event assignment if you don’t need them. 4HEEVENTPARAMETERSPASSEDINCLUDEAREFERENCETOTHEDPPL=llhe_]pekj object, which in turn GIVESYOUACCESSTOTHEDppl?kjpatpOBJECT5SINGTHEEjep method, you can hook up to Dppl=llhe_]pekj EVENTS&OREXAMPLE IFYOUWANTTOHOOKTHE=qpdajpe_]paNamqaopEVENTTOAMODULE YOUWOULDDOSOAS SHOWNIN,ISTING  Listing 3-3. Simple Implementation of an HTTP Module lq^he__h]oo>]oe_=qpd?qopkiIk`qha6EDpplIk`qha w lq^he_rke`Ejep$Dppl=llhe_]pekj]llhe_]pekj% w ]llhe_]pekj*=qpdajpe_]paNamqaop'9± jasArajpD]j`han$pdeo*Kj=qpdajpe_]paNamqaop%7 y lq^he_rke`@eolkoa$%wy lq^he_rke`Kj=qpdajpe_]paNamqaop$k^fa_pokqn_a(Araj)p=ncoarajp=nco% w Dppl=llhe_]pekj]ll9$Dppl=llhe_]pekj%okqn_a7 Dppl?kjpatp?kjpatp9Dppl?kjpatp*?qnnajp7 ++]j`]_pekj y

C H A P T E R 3 N M O D U LE S A N D H A N D LE R S

2EMEMBERTHATYOURMODULEHASACCESSTOTHEDppl?kjpatp object and from there to all other intrinsic ASP.NET pipeline objects, such as Naolkjoa and Namqaop&ROMHERE YOUCANRETRIEVEINPUT CREATECONTENT ANDSOFORTH(OWEVER KEEPINMINDTHATCERTAINTHINGSMAYNOTBEAVAILABLEUNTIL further down the chain. 9OUCANHOOKASMANYEVENTSASYOULIKEINTHEEjep method so that your module is able to manage multiple operations with different functions. It is tidier to separate differing logic into separate modules. This ensures that the modules are, indeed, modular, as their name implies. In many CASES ANYFUNCTIONALITYTHATYOUIMPLEMENTCOULDREQUIREHOOKINGMULTIPLEEVENTS&OREXAMPLE a logging filter might log the start time of a request in >acejNamqaop and then write the request completion into the log in Aj`Namqaop.

NCaution Modules work deep inside the processing pipeline. Calling certain methods can prevent the pipeline from proceeding to the next step. In particular, Naolkjoa*Aj` and =llhe_]pekj*?kilhapaNamqaop complete the request and force the pipeline to end, thus skipping all subsequent steps. The pipeline will return control to the Web Server and no further modules will be invoked. A better practice is to leave the pipeline running, but use a context variable to inform subsequent modules not to execute. The purpose of the @eolkoa method is to clean up any resources when the module unloads ANDTORELEASEOTHERRESOURCESBEFORETHEGARBAGECOLLECTORFINALIZESTHEMODULEINSTANCE)FTHEREIS NOTHINGTODISPOSE LEAVETHEMETHODBODYBLANK The Ejep methodISTHEMAINMETHODOFINTEREST(ERE YOUCANINITIALIZEYOURMODULEANDWIRE ITUPTOONEORMOREREQUEST PROCESSINGEVENTSAVAILABLEONTHEDppl=llhe_]pekj class. Keep in mind THATEVENTSFIREWHENTHEAPPROPRIATESTEPINTHEPIPELINEISREACHED INADEFINEDORDER ANDINCONJUNCTIONWITHOTHERMODULES7ITHOUTACLEARUNDERSTANDINGOFTHEPIPELINEARCHITECTUREEXPLAINED IN#HAPTER YOULLHAVEDIFFICULTYWRITINGSOPHISTICATEDMODULESTHAT perform well.

Example—Check for a Specific Header The following example checks for a specific header, called a referrer WHICHPROVIDESINFORMATION ABOUTTHEREFERRINGPAGE0ARADOXICALLY THEREFERRERISNAMEDhREFERRERv$ONTWORRYABOUTTHEMISspelled word (the sidebar explains more).

WIKIPEDIA ON THE WORD REFERER Referer is a common misspelling of the word referrer. It is so common, in fact, that it made it into the official specification of HTTP—the communication protocol of the World Wide Web—and has therefore become a widely used industry spelling when discussing HTTP referrers. The misspelling usage is not universal; the correct spelling of “referrer” occurs in some web specifications, such as the Document Object Model. [Source: dppl6++aj*segela`e]*knc+sege+Nabanan]

)ADVISEYOUTOPAYATTENTIONTOWHICHWORDYOUREUSING


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In this example, you’ll look for a specific referrerORREFERRINGPAGEˆTHE52,OFTHEPREVIOUS page. (It’s the page containing the link to the page you’re currently processing.) The usage of the HEADERISVOLUNTARY ACCORDINGTO(440STANDARDS BUTMOSTSITESUSEITTOTRACKUSERSORMANAGE LOGGING(OWEVER SOMEPAGESARENOTINTENDEDTOBECALLEDFROMOUTSIDEOURSITE)FLINKEDFROM another page within our application, such pages will execute correctly, but if linked from anywhere else, you’ll treat that as an exception. Such external links typically occur when a user bookmarks ASPECIFICPAGEDEEPWITHINYOURAPPLICATION7HENATTEMPTINGTOOPENONEOFTHESEPAGES ITISNOT POSSIBLE BECAUSETHEREARESEVERALPREREQUISITESTEPSTOCOMPLETEBEFOREHAND5SINGAMODULELIKE THEONEIN,ISTING  YOUCANCAPTURETHESEREQUESTSOUTSIDETHECOMMONPAGECODEANDREDIRECT users to a suitable page, such as one that explains appropriate usage of bookmarks. Listing 3-4. An HTTP Module That Looks for the Referer Header lq^he__h]ooNabannanIk`qha6EDpplIk`qha w nacekjEDpplIk`qhaIai^ano lq^he_rke`@eolkoa$% w ++_ha]j)ql_k`adana* y lq^he_rke`Ejep$Dppl=llhe_]pekj_kjpatp% w _kjpatp*LnaNamqaopD]j`hanAta_qpa'9± jasArajpD]j`han$_kjpatp[LnaNamqaopD]j`hanAta_qpa%7 y rke`_kjpatp[LnaNamqaopD]j`hanAta_qpa$k^fa_poaj`an(Arajp=ncoa% w Dppl=llhe_]pekj]ll9$Dppl=llhe_]pekj%oaj`an7 DpplNamqaopnamqaop9]ll*?kjpatp*Namqaop7 eb$namqaop*Qnh*Hk_]hL]pd*Aj`oSepd$@ab]qhp*]olt%% w eb$Opnejc*EoJqhhKnAilpu$namqaop*Da]`anoWNabananY%% w pdnksjasDpplAt_alpekj$0,/(>kkgi]ngejceojkp]hhksa`%7 y y y aj`nacekj y 4HISCODEASSUMESTHATYOUHAVEAPAGECALLEDORATLEASTENDINGWITHh$EFAULTASPXvLINKINGTO another page in your application. The name of the other page doesn’t matter. To test this module: 1. Configure web.configTOACTIVATETHEMODULE 2. #REATETWOPAGES $EFAULTASPXAND2EFERER4ESTASPX$EFAULTASPXHASAHYPERLINKTO 2EFERER4ESTASPX 3. #OMPILEANDSTARTTHEAPPLICATIONBYLAUNCHINGTHE$EFAULTASPXPAGE

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4. #LICKTHEHYPERLINKON$EFAULTASPXˆTHE2EFERER4ESTASPXPAGEISDISPLAYED 5. "OOKMARKTHE2EFERER4ESTASPXPAGE 6. Close your browser, reopen it, and load the bookmark, then press F5 to force a refresh of the PAGEFROMTHESERVER 7. !NEXCEPTIONOCCURSANDTHEBROWSERSHOWSAERROR 9OUMIGHTINSISTTHATALLOFTHISCANBEACCOMPLISHEDONTHEPAGELEVELUSINGCONVENTIONAL CODE4HISISCORRECT BUTFUNDAMENTALTASKSAREBESTHANDLEDONAFUNDAMENTALLEVEL)NADDITION INTERCEPTINGLOW LEVELEVENTSTOHANDLELOW LEVELACTIONISFASTER MORESECURE ANDMORERELIABLE !DDINGMOREPAGESWITHTHESAMEBEHAVIORDOESNOTREQUIREANYCHANGETOTHECODE)TSIMPLY works because the module tests all pages in the application.

Interaction Between Modules 7RITINGPRIVATEMODULESISAPOWERFULTECHNIQUEFOREXTENDING!30.%4(OWEVER EXTENDINGCAN mean replacing existing functionality. Sometimes a smart solution results simply from using the internal modules and your own module together. To begin, you’ll need access to the internal modules at runtime. You should make connections in the EjepEVENTINORDERTOHAVEACCESSATANEARLYSTAGE,ISTING SHOWSYOUHOWTORETRIEVE information about internal modules, and other kinds of modules, attached to the pipeline so far. Listing 3-5. Retrieving Information About Modules lq^he__h]ooOaooekjHkcIk`qha6EDpplIk`qha w nacekjEDpplIk`qhaIai^ano lq^he_rke`@eolkoa$% w y lq^he_rke`Ejep$Dppl=llhe_]pekj]llhe_]pekj% w Dppl?kjpatp_kjpatp9Dppl?kjpatp*?qnnajp7 bkna]_d$opnejcgauej]llhe_]pekj*Ik`qhao*=hhGauo% w _kjpatp*Naolkjoa*Snepa$Opnejc*Bkni]p$w,y9w-yw.y8^n:( gau( ]llhe_]pekj*Ik`qhaoWgauY*CapPula$%*EoLq^he_;lq^he_6ejpanj]h( ]llhe_]pekj*Ik`qhaoWgauY*CapPula$%*=ooai^huMq]hebea`J]ia%%7 y y aj`nacekj y

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The current context is used to output the text directly into the current page where the request is handled. You can use the Ik`qhao property to get a list of the modules and where they are defined (see Figure 3-3).

Figure 3-3. Modules already available You probably need to use this method of getting access to an embedded module, as not all MODULESOFFERDIRECTACCESSTOTHEIRSTATESANDEVENTS/NCEYOUKNOWTHENAMEANDTYPEOFASPEcific module, you can cast the type and get the object you need.

Configuration and Deployment Now that the module is implemented, you can compile it into an assembly that ASP.NET is able to load at runtime. This is straightforward as long as the module is in the web application. No SPECIALACTIONISREQUIRED9OUWILLPROBABLYWANTTOCREATESEVERALMODULESANDHAVETHEMINDIFferent assemblies for easy reuse. The assemblies will need to be referenced by your web project. To CONSTRUCTSUCHAMODULE CHOOSEh#LASS,IBRARYvASTHEPROJECTTEMPLATE2EMOVETHEDEFAULTCLASS CREATEDBYTHETEMPLATE ANDADDANOBJECTOFTYPEh!30.%4-ODULEvASSHOWNIN&IGURE 

Figure 3-4. Add a module to current project.

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Configuring the Default Web Server and Development Environment To test the module, you’ll need to configure the settings in web.config. Place the appropriate lines in the 8ouopai*sa^: section: 8dpplIk`qhao: 8]``j]ia9NabannanIk`qha pula9=lnaoo*Atpajoe^ehepu*DpplIk`qhao*NabannanIk`qha+: 8+dpplIk`qhao: 4HESETTINGSFORTHEDEVELOPMENTENVIRONMENTALSOAPPLYFOR))3 ))3 AND))3INCLASSIC MODE4HEREARESEVERALADVANTAGESTORUNNINGTHE))3INTEGRATEDPIPELINEHOWEVER THATREQUIRES different settings, asSHOWNIN4ABLE  Table 3-10. Options of the httpModule Settings

Attribute

Typical Values

j]ia

any string

Description The module name that appears in settings dialogs

pula

class, assembly

-ODULETYPE

Configuring IIS7 Settings In the main (web) project, add a reference to the project containing the module. Assuming the namespace of the external project is =lnaoo*Atpajoe^ehepu*DpplD]j`han*IuD]j`han, add the following to web.config: 8ouopai*sa^Oanran: 8ik`qhao: 8]``j]ia9NabannanIk`qha pula9=lnaoo*Atpajoe^ehepu*DpplD]j`han*IuD]j`hannaokqn_aPula9Beha namqena=__aoo9Na]`lna?kj`epekj9ejpacn]pa`Ik`a+: 8+ik`qhao: 8+ouopai*sa^Oanran: Compile both the project containing the module and the web project. Add the mapping in )NTERNET)NFORMATION3ERVICES-ANAGER4HEMAPPINGWILLNOWFUNCTIONPERFECTLYFORBOTHTHEDEVELOPMENTENVIRONMENTANDDIRECTUSAGE from the local IIS7 (see Table 3-11). Table 3-11. Options for the Module Settings for IIS7 Integrated Mode

Attribute

Typical Values

Description

j]ia

any string

The module name that appears in settings dialogs.

lna_kj`epekj

string

Specifies conditions under which the module will run. This is usually the name of another handler or module required to run before this one.

pula

class, assembly

Type information of the handlers definition.

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Configure Using IIS Management Console 2ATHERTHAN adding the IIS7 integrated mode settings to web.config YOUCANSIMPLYUSETHE))3-ANagement Console. The settings correspond directly. Altering web.config will result in an immediate CHANGETOTHE-ANAGEMENT#ONSOLESETTINGS ANDVICEVERSA4OCONFIGUREUSINGTHE))3-ANAGEment Console: 1. /PEN)NTERNET)NFORMATION3ERVICE-ANAGER 2. /PENTHEWEBYOUWANTTOCHANGE 3. )NTHE))3SECTION DOUBLE CLICKONTHE-ODULESICON 4. #LICKON!DD-ANAGED-ODULEINTHETASKLISTTOTHERIGHT 5. %NTERTHESEVALUESINTHEDIALOGANDCLOSETHEDIALOGBYCLICKING/+ THEN a. 'IVETHEMODULEANAPPROPRIATENAME b. /PENTHETYPEDROP DOWNANDSELECTTHEMODULESTYPE 6. #LOSETHEMAINDIALOGBYPRESSING/+ No restartISREQUIREDTOACTIVATE the new settings.

Handlers This sectionFOCUSESONDEVELOPING(440HANDLERSFOR))3 USING the .NET Framework. You’ll look ATWHENITISAPPROPRIATETODEVELOPAN))3HANDLER rather than a module.

Built-In Handlers ASP.NET offersSEVERALDEFAULT(440HANDLERS

s 0AGE(ANDLERASPX : Handles web pages



s 5SER#ONTROL(ANDLERASCX (ANDLES7EBUSERCONTROLPAGES



s 7EB3ERVICE(ANDLERASMX (ANDLES7EB3ERVICEPAGES



s 4RACE(ANDLERTRACEAXD : Handles trace functionality



s !SSEMBLY2ESOURCE,OADER7EB2ESOURCEAXD : Handles embedded resources in assemblies



s 3CRIPTRESOURCEHANDLER3CRIPT2ESOURCEAXD : Handles the scripting support for AJAXenabled projects



s &ORBIDDEN(ANDLERCONFIG $ENIESACCESSTOFILESTHATCONTAINCONFIDENTIALINFORMATION

The IIS configuration defines the assignments. You will also find other assignments there. Extensions such as .tkih, *nai, *ok]l, and *or_RELATETOTHECAPABILITIESPROVIDEDBY7INDOWS #OMMUNICATION&OUNDATION7#& AND its predecessor, .NET remoting.

Extending ASP.NET Using Http Handlers 7HILEMODULESARELOWLEVEL ANDRUNAGAINSTEVERYINBOUND request to the ASP.NET application, HTTP handlers focus more on a specific request mapping. This is usually a mapping of a file extension.

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(440HANDLERIMPLEMENTATIONSAREVERYSIMPLEINTHEIRCONCEPT BUTHAVINGACCESS to the Dppl?kjpatpOBJECTENABLESENORMOUSVERSATILITY(ANDLERSAREIMPLEMENTEDTHROUGHTHE EDpplD]j`han interface, or its asynchronous counterpart, EDppl=ouj_D]j`han. The interface consists of a single method, Lnk_aooNamqaop, and a single property, EoNaqo]^ha4HEASYNCHRONOUSVERSION has a pair of methods (>acejLnk_aooNamqaop and Aj`Lnk_aooNamqaop) and the same EoNaqo]^ha propERTY4HEVITALINGREDIENTISLnk_aooNamqaop WHICHRECEIVESANINSTANCEOFTHEDppl?kjpatp object. 4HISSINGLEMETHODISRESPONSIBLEFORHANDLINGA7EBREQUESTFROMSTARTTOFINISH (OWEVER SIMPLEDOESNOTIMPLYSIMPLISTIC!SYOUMAYKNOW THEREGULARPAGEPROCESSINGCODE ANDTHE7EB3ERVICEPROCESSINGCODEAREIMPLEMENTEDASHANDLERS"OTHAREANYTHINGBUTSIMPLE Their power originates from the Dppl?kjpatp object, which has access to both the request informaTIONANDTHERESPONSEDATA4HISMEANSTHAT LIKEA7EB3ERVER AHANDLERCANCONTROLTHEWHOLE PROCESSONITSOWN7HATEVERYOUWANTTOIMPLEMENTONTHELEVELOFSPECIFICMAPPINGISACHIEVABLE using handlers.

Scenarios to Use HTTP Handlers To betterUNDERSTANDTHEPOWEROFHANDLERS LETSTAKEALOOKATWHATOTHERSHAVEIMPLEMENTEDON top of EDpplD]j`han:

s #REATINGDYNAMICIMAGES



s 7ATERMARKINGEXISTINGIMAGES



s h0RETTYPRINTINGvOFTHEPAGESSOURCECODE



s 'ENERATINGDYNAMICCONTENTPULLEDFROMADATABASEOREXTERNALRESOURCE



s 4RANSFORMINGCONTENTFROMOTHERRESOURCES SUCHAS8-,INTO(4-,



s %XTRACTINGRESOURCESFROMASSEMBLIESONTHEFLY



s 2EDIRECTINGTOFROM33,



s )MPLEMENTING0INGBACKAND4RACKBACKCAPABILITIES EVENIFTHESITEISNOTABLOG

!DDITIONALLY YOUCANIMPLEMENTHANDLERSASYNCHRONOUSLY4HISVASTLYEXTENDSTHEPOTENTIAL usage scenarios. Since asynchronous calls are closely related to threading and performance, you looked at threading and how it could benefit from asynchronous programming in Chapter 2. In this section, I will focus more on common usages of basic HTTP handler implementations.

Getting Started For an HTTP handler, all the action occurs through a single call to Lnk_aooNamqaop. This can be as simple as: lq^he_rke`Lnk_aooNamqaop$Dppl?kjpatp_kjpatp% w _kjpatp*Naolkjoa*Snepa$DahhkSknh`%7 y 5SINGTHEDppl?kjpatpOBJECT YOUHAVEACCESSTOTHENamqaop, Naolkjoa, Oaooekj, and ?]_da OBJECTS9OUHAVEALLTHEKEYFEATURESOFAN!30.%4REQUESTATYOURDISPOSAL ANDYOUCANUSETHISTO DETERMINEWHATUSERSSUBMITTEDANDTORETURNCONTENTBACKTOTHECLIENT2EFERTO#HAPTERTOSEE why Dppl?kjpatp plays such an important role in the request-processing process.)

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The key operation of the handler is to write output into the Naolkjoa object—or, more specifically, the Naolkjoa object’s KqplqpOpna]i. This output is sent back to the client. Behind the scenes—for IIS6 or classic mode—the EO=LESknganNamqaop sends the KqplqpOpna]i back to the ISAPI a_^*Snepa?heajp METHOD WHICHACTUALLYPERFORMSTHE))3OUTPUTGENERATION&OR))3)NTEGRATED-ODETHEPIPELINEIS responsible to handle the KqplqpOpna]i object. Again, refer to Chapters 1 and 2 to learn more about these steps.

Building a Handler Now, let’s build a simple handler. To do this, you define a class, which implements the Ouopai*Sa^* EDpplD]j`han interface. $ESPITETHEPROMINENCEOFTHELnk_aooNamqaop method, you’ll also need to implement a property—EoNaqo]^ha4HISPROPERTY WHICHRETURNSA"OOLEANVALUE INDICATESWHETHERTHEINSTANCE can be reused for subsequent requests. In some cases, after processing a request, your handler may NOTBEINAVALIDSTATEFORPROCESSINGFURTHERREQUESTSˆESPECIALLYIFDATAABOUTTHEPREVIOUSREQUEST WASSTOREDINMEMBERVARIABLES4HISISBECAUSETHE!30.%4RUNTIMECANHANDLEMANYREQUESTSAT THESAMETIME!SLONGASTHEREARETHREADSAVAILABLEINTHETHREADPOOL ANEWREQUESTWILLBEPROCESSEDEVENIFANOTHERONEISSTILLRUNNING%ACHTHREADREQUIRESANEWINSTANCEOFTHEHANDLER EVEN IFTHEHANDLERISMARKEDhISREUSABLEv7HENAREQUESTISCOMPLETE THECURRENTHANDLERINSTANCEIS RETAINEDINMEMORYANDREUSEDFORTHENEXTREQUEST4HISCANLEADTOODDBEHAVIOR DEPENDINGON the workload and on the existence of other instances of the handler. Such problems can be unpreDICTABLEANDDIFFICULTTOSIMULATEORRECOGNIZEINADEVELOPMENTENVIRONMENT &ORSTABLEANDRELIABLEBEHAVIOR YOUMIGHTASSUMETHATSETTINGTHEEoNaqo]^ha property to b]hoa is the solution. After all, this would create a new instance of the object any time a request is ABOUTTOBEPROCESSED(OWEVER DEPENDINGONHOWhINTENSIVEvYOURCODEIS THISCANLEADTOHIGHER MEMORYCONSUMPTION MORE#05WORKLOAD ANDLESSTHROUGHPUT4HEREISNOSTRICTRULEABOUTIT BUT reusing the instances is the preferred solution. Keep in mind that access to members is not exactly WHATYOUMIGHTEXPECT4HEREFORE ITISADVISABLETOAVOIDPRIVATEMEMBERSTHATHOLDDATA IFPOSSIBLE)FYOUSTILLWISHTOUSEMEMBERVARIABLES REMEMBERTHATTHEYNEEDTOBETHREADSAFE7HEN REPLACINGREGULARMEMBERSWITHSTATICMETHODS YOULLHAVETOIMPLEMENTTHREADSAFECODE)FANY of these requirements cannot be fulfilled, you should set EoNaqo]^ha to b]hoa/THERWISE THEIMPLEmentation will look like the following: lq^he_^kkhEoNaqo]^ha w cap w napqnjpnqa7 y y EoNaqo]^haSHOULDBEACONSTANT#HANGINGTHEVALUEDURINGPROCESSINGWOULDNOTHAVEANY EFFECT ASTHEVALUEISREADONCETHE handler is instantiated.

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The Entry Point The Lnk_aooNamqaop method is the main entry point for the handler. Its role is to work off the request specified by the DpplNamqaopINSTANCE FROMTHEPROVIDEDDppl?kjpatp instance, and generate an appropriate response using the DpplNaolkjoa instance. The Lnk_aooNamqaopMETHODISINVOKEDBY the .NET runtime during the Ata_qpaNamqaopD]j`han request processing stage, assuming that the mapping is able to route the request to the specific handler. This is in contrast to modules, which RECEIVEALLREQUESTSPASSINGTHROUGHTHEPIPELINE Finally, let’s implement the Lnk_aooNamqaop method, so that our handler has something to do. 4OKEEPTHINGSSIMPLE OURHANDLERWILLRETURNTHECURRENTTIMEOFTHESERVER9OUCANSPECIFYTHE TIMEZONEINTHEQUERYSTRING/URGOALISTOREQUESTA52, SUCHASdppl6++iuoanran+l]ca*peia, and OBTAINTHECURRENTTIMEOFTHESERVER)NADDITION YOUCANGETTHEUNIVERSALCOORDINATEDTIME54# by requesting dppl6++iuoanran+l]ca*peia;qp_9pnqa,ISTING SHOWSTHEIMPLEMENTATION Listing 3-6. Simple Handler Mapped to a New *.time File Extension lq^he__h]ooPeiaD]j`han6EDpplD]j`han w nacekjEDpplD]j`hanIai^ano lq^he_^kkhEoNaqo]^ha w capwnapqnjpnqa7y y lq^he_rke`Lnk_aooNamqaop$Dppl?kjpatp_kjpatp% w @]paPeia`p7 opnejcqoaQp_9_kjpatp*Namqaop*MqanuOpnejcWqp_Y7 eb$Opnejc*EoJqhhKnAilpu$qoaQp_%""qoaQp_*Amq]ho$pnqa%% w `p9@]paPeia*Qp_Jks7 y ahoa w `p9@]paPeia*Jks7 y _kjpatp*Naolkjoa*Snepa$± Opnejc*Bkni]p$8dpih:8^k`u:8d-:w,y8+d-:8+^k`u:8+dpih:(± `p*PkHkjcPeiaOpnejc$%± %%7 y aj`nacekj y !SYOUASSIGNTHISHANDLERTOASPECIFICEXTENSIONˆTIMEˆYOULLONLYRECEIVEITWHENTHECLIENT USESTHISSPECIFIC52,4HERESPONSEISSIMPLEANDCREATESASMALL(4-,PAGE9OUCOULDEVENTAILOR the response to suit clients that are not browsers.

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You use the DpplNamqaop*MqanuOpnejcCOLLECTIONTORETRIEVEAQUERYSTRINGVARIABLE AND write the current time in response using the DpplNaolkjoa*Snepa method. I recommend using the KqplqpOpna]i if other handlers are processing the request, or if you want to add to the existing RESPONSE)NTHEPREVIOUSEXAMPLE YOUWRITEACOMPLETERESPONSEINTHEONEHANDLER ANDTHUS the SnepaMETHODISAPPROPRIATE&IGURE SHOWSHOWTOADDAMODULEUSINGTHE))3-ANAGER

Figure 3-5. Setting the mapping of a managed handler in IIS7 ))3DOESNOTREQUIREARESTARTORANYOTHERACTIONINORDERTOACTIVATETHEHANDLER!REQUESTTHAT uses the mapped extension should work immediately.

Example—Image Handler !VERYCOMMON scenario for handlers is the manipulation of images. As with any other resource, a browser obtains an image by sending a GET request. Handling large numbers of images at multiple resolutions can be a challenge. Imagine a web shop with thousands of product images stored at one RESOLUTION(OWEVER DIFFERENTIMAGESIZESAREREQUIREDTHROUGHOUTTHESITE FROMCATALOGTHUMBNAILS TOLARGEPREVIEWPANESANDICONSINTHESHOPPINGBASKET#ONVERTINGALLTHESEIMAGESINTOSEVERALDIFFERENTSIZESCOULDBEEXPENSIVE EVENWITHABATCHSCRIPT)MAGESCHANGEFREQUENTLY ANDMAINTAINING ALLCURRENTPICTURESINMANYDIFFERENTSOURCESIZESISANIMAGEMANAGEMENTHEADACHE!DDITIONALLY a watermark is added to the image to protect the intellectual properties of the image’s owner. 7RITINGCODEANDCREATINGIMAGESDYNAMICALLYISATYPICALTASKFORAHANDLER!TTACHINGREQUESTS TOANIMAGECOULDBEACHIEVEDBYUSINGAPATHFILTERLIKE&*ljc,ISTING SHOWSHOWEASYITISTO manipulate content and send it to a client.

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Listing 3-7. Adding a Watermark to an Image and Resizing It Using a Handler j]iaol]_a=lnaoo*Atpajoe^ehepu*DpplD]j`han w lq^he__h]ooEi]caD]j`han6EDpplD]j`han w nacekjEDpplD]j`hanIai^ano lner]pa_kjopbhk]pBKJPOEVA93.B7 lner]pa_kjopopnejcBKJP9Ran`]j]7 lner]pa_kjopopnejcPATP9S]pani]ng7 lq^he_^kkhEoNaqo]^ha w capwnapqnjpnqa7y y lq^he_rke`Lnk_aooNamqaop$Dppl?kjpatp_kjpatp% w ++`apanieja]jei]canamqaop eb$$L]pd*Cap@ena_pknuJ]ia$± _kjpatp*Namqaop*Qnh*=^okhqpaL]pd%%*Aj`oSepd$Ei]cao%% w ++hk]`ei]ca]j`]``s]pani]ng >epi]leic9$>epi]l%>epi]l*BnkiBeha$± _kjpatp*Oanran*I]lL]pd$_kjpatp*Namqaop*Qnh*=^okhqpaL]pd%%7 Cn]lde_oc9Cn]lde_o*BnkiEi]ca$eic%7 >nqod^9jasOkhe`>nqod$?khkn*Oehran%7 Bkjpb9jasBkjp$BKJP(BKJPOEVA%7 OevaBopnejcIa]oqna9c*Ia]oqnaOpnejc$PATP(b%7 ++_]h_qh]papdaopnejclkoepekjpk_ajpankqplqp bhk]pt(u7 t9eic*Se`pd+.)opnejcIa]oqna*Se`pd+.7 u9eic*Daecdp+.)opnejcIa]oqna*Daecdp+.7 c*@n]sOpnejc$PATP(jasBkjp$BKJP(BKJPOEVA%(^(t(u%7 ++naoevapklnkre`a``]p]$bnkiMqanuOpnejc% eb$_kjpatp*Namqaop*MqanuOpnejcWsY9jqhh"" _kjpatp*Namqaop*MqanuOpnejcWdY9jqhh% w ejps(d7 eb$Ejp/.*PnuL]noa$_kjpatp*Namqaop*MqanuOpnejcWsY(kqps%"" Ejp/.*PnuL]noa$_kjpatp*Namqaop*MqanuOpnejcWdY(kqpd%% w eic9$>epi]l%eic*CapPdqi^j]ehEi]ca$s(d(jqhh(EjpLpn*Vank%7 y y ++kqplqppkpdanaolkjoaopna]i eic*O]ra$_kjpatp*Naolkjoa*KqplqpOpna]i(Ei]caBkni]p*Flac%7 eic*@eolkoa$%7 y y y aj`nacekj y y

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4HEHANDLERFIRSTCHECKSTHATITISDEALINGWITHAFILEFROMAPARTICULARDIRECTORYSEE,ISTING   7HILETHEFILEMAPPINGFORCESTHEHANDLERTORUNFOREVERYREQUESTFORANIMAGEWITHTHESPECIFIED extension, this test restricts the special processing to images in the “Images” folder only. The handler LOADSTHEIMAGEFROMDISK RESOLVINGTHELOCALPATHVIAOanran*I]lL]pd. Then it applies the watermark to the image. The Ia]oqnaOpnejc methodMEASURESTHESTRINGSIZEINORDERTOALIGNITWITHTHEIMAGE SOTHATTHETEXTAPPEARSCENTEREDHORIZONTALLYANDVERTICALLY3TREAMSSIMPLIFYTHEOUTPUTOFTHEIMAGE The O]raMETHODSENDSTHEOUTPUTDIRECTLYINTOANOUTPUTSTREAMIN*0%'FORMAT$ISPOSINGOFTHE IMAGEISREQUIRED ASFREQUENTUSEOFAHANDLERONASYSTEMWITHHIGHWORKLOADCOULDPREVENTTHEGARbage collector from freeing the memory often enough. Listing 3-8. The Handler Is As Easy to Use As Any Other Image Resource 8]ol6Ei]canqj]p9oanranE@9eic-Ei]caQnh9z+Ei]cao+Eic-*ljc+:8^n+: 8]ol6Ei]canqj]p9oanranE@9Ei]ca-Ei]caQnh9z+Ei]cao+Eic-*ljc;s9-,,"d9-,,+: Figure 3-6 shows the output of the watermarked and thumbnail images.

Figure 3-6. Add a watermark to an image on the fly or create a thumbnail. $YNAMICIMAGEMANIPULATIONISPOWERFULANDFLEXIBLE ANDTHEREARENUMEROUSPOSSIBILITIESFOR using an image handler in your applications. The final step in creating such a handler is to configure it in web.config0LEASEREFERTOTHESECTIONh#ONFIGURATIONAND$EPLOYMENTvTOREADMOREABOUT the VARIOUSSETTINGS

C H A P T E R 3 N M O D U LE S A N D H A N D LE R S

Example—Read Dynamic CSS from Resource )N,ISTING  )DESCRIBEAHANDLERTHATLOADSSTYLESHEETSSTOREDASEMBEDDEDRESOURCESINAN ASSEMBLY)TREPLACESANYCALLTOASTYLESHEETBYDELIVERINGASPECIFICCSSFILE4HEDEFINITIONINTHE web.config looks like this: 8]``ran^9CAPl]pd9&*_oopula9=lnaoo*Atpajoe^ehepu*DpplD]j`han*?ooD]j`han+: 3EETHESECTIONh#ONFIGURATIONAND$EPLOYMENTvFORMOREINFORMATIONABOUTCONFIGURING a handler for the IIS7 integrated mode. 4OOBTAINTHESTYLEFILES THEYMUSTBEMARKEDASANEMBEDDEDRESOURCE4HEREARESEVERALWAYS to handle data from sources other than the file system (see Figure 3-7).

. Figure 3-7. To handle files as embedded resources, use the file’s Property box. 4HECODEITSELFDOESNOTHAVEANYQUIRKS)TPROCESSESWHATEVERITENCOUNTERS ANDDECIDESHOW to proceed from the information in Dppl?kjpatpSEE,ISTING  

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Listing 3-9. Dynamic Handling of CSS from Embedded Resources lq^he__h]oo?ooD]j`han6EDpplD]j`han w nacekjEDpplD]j`hanIai^ano lq^he_^kkhEoNaqo]^ha w capwnapqnjb]hoa7y y lq^he_rke`Lnk_aooNamqaop$Dppl?kjpatp_kjpatp% w Qji]j]ca`IaiknuOpna]io7 eb$_kjpatp*Namqaop*Qoan=cajp9jqhh"" _kjpatp*Namqaop*Qoan=cajp*?kjp]ejo$IOEA%% w o9$Qji]j]ca`IaiknuOpna]i%± pdeo*CapPula$%*=ooai^hu*CapI]jebaopNaokqn_aOpna]i$± =lnaoo*DppD]j`han*D]j`han=ooai^hu*?oo*ea*_oo%7 y ahoa w o9$Qji]j]ca`IaiknuOpna]i%± pdeo*CapPula$%*=ooai^hu*CapI]jebaopNaokqn_aOpna]i$± =lnaoo*DppD]j`han*D]j`han=ooai^hu*?oo*bb*_oo%7 y o*Oaag$,(OaagKnecej*>acej%7 qoejc$IaiknuOpna]iio9jasIaiknuOpna]i$$ejp%o*Hajcpd%% w ^upaWY^qbban9jas^upaWo*HajcpdY7 o*Na]`$^qbban(,(^qbban*Hajcpd%7 io*Snepa$^qbban(,(^qbban*Hajcpd%7 io*SnepaPk$_kjpatp*Naolkjoa*KqplqpOpna]i%7 y y aj`nacekj y First, let’s locate the current user agent in this code by using the property Qoan=cajp of the DpplNamqaop object. If the Qoan=cajpISh-3)% vINDICATINGAN)NTERNET%XPLORERBROWSER THENTHE RESOURCENAMEDhIECSSvISRETRIEVEDFROMTHEASSEMBLY&ORANYOTHERQoan=cajpo, “ff.css” is loaded instead. The stream is copied to a IaiknuOpna]i object. The IaiknuOpna]i is helpful, as it is able to copy its own content to another stream by using the SnepaPk method. In the case of a handler, this is THEOUTPUTSTREAMPROVIDEDBYTHEDpplNaolkjoa object through the Naolkjoa property. This technique can be reused. By looking for specific file extensions and for the “user-agent” header, you can block certain clients from reading the content of these resources or supply them WITHAREPLACEMENTRESOURCE!LTERNATIVELY READINGRESOURCESFROMADATABASEINSTEADOFANASSEMBLYGIVESMOREFLEXIBILITYWITHOUTADDINGCODETOTHEPAGESTHEMSELVES

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USING WEB RESOURCES The example shown in this section is just to explain typical scenarios for HTTP handlers. Especially regarding web resource management, the preferred method for storing and retrieving resources is the embedding of web resources. Using an assembly bound attribute, you can add any kind of data to the assembly: W]ooai^hu6Sa^Naokqn_a$?oo*ea*_oo(patp+_oo%Y W]ooai^hu6Sa^Naokqn_a$?oo*bb*_oo(patp+_oo%Y An embedded handler for the designated *]t` extension retrieves the resources from server. The URL uses two query string values, “d” and “t”. “d” takes an encrypted ID of that value and “t” a time stamp. To retrieve such a resource, you can create the URL, using the following code snippet from a page: ?heajpO_nelpI]j]can_o9L]ca*?heajpO_nelp7 PulanoPula9pdeo*CapPula$%7 DpihHejgdh?oo9jasDpihHejg$%7 dh?oo*Dnab9_o*CapSa^Naokqn_aQnh$noPula(?oo*ea*_oo%7 pdeo*?kjpnkho*=``$dh?oo%7 The call of the CapSa^Naokqn_aQnh method assures that the parameters for query string are set properly.

Example—Handler That Does Not Create Content Handlers usuallyCREATECONTENTˆTYPICALLY(4-,ORDATATHATBUILDSANIMAGE(OWEVER ITSNOT IMPERATIVE(ANDLERSAREPRIMARILYINVOKEDBYTHEASSOCIATEDFILEEXTENSION)MAGINEYOUDEFINE a custom extension named “.counter” and associate it with a handler. Your handler might execute SOMECODE BUTIGNORETHE7RITERANDNOTSENDANYTHINGBACKTOTHECLIENT!NOTHERIDEAISTOONLY WRITEDATATOTHECLIENTWHENYOURUNTHEHANDLERINDEBUGMODEANDSAVEBANDWIDTHWHENRUNNING ONAPRODUCTIONSERVER7HETHERORNOTTHEOUTPUTISREQUIRED YOULLSTILLHAVETOINVOKETHEHANDLER BYISSUINGA'%4OR0/34REQUESTTOTHESERVER4HEREFORE YOULLNEEDANELEMENTTHATCANFORCETHE browser to create such a request. There are only a few ways to do this:

s )MAGEELEMENT



s &ORMELEMENT



s )&RAMEELEMENT



s *AVA3CRIPTCODE

)MUSINGAN)&2!-%ELEMENT in the following example, because I want to show the content WHENINDEBUGMODE ANDLEAVETHECONTENTEMPTY OTHERWISE4HEDEFINITIONOFTHE)&2!-%DEMONSTRATESHOWYOUINVOKETHEHANDLER ASSHOWNIN,ISTING  Listing 3-10. Invoke a Handler Using a Registered Extension 8ebn]iaon_9iu*_kqjpanse`pd9-,,daecdp91,o_nkhhejc9jk:8+ebn]ia: Furthermore, the handler itself shows the processing within the Lnk_aooNamqaop method (see ,ISTING  

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Listing 3-11. Code of the Handler lq^he__h]oo?kqjpanD]j`han6EDpplD]j`han w nacekjEDpplD]j`hanIai^ano lq^he_^kkhEoNaqo]^ha w capwnapqnjpnqa7y y lq^he_rke`Lnk_aooNamqaop$Dppl?kjpatp_kjpatp% w opnejcl]pd9_kjpatp*Namqaop*QnhNabannan*Hk_]hL]pd7 opnejcbeha9_kjpatp*Oanran*I]lL]pd$?kqjpan*tih%7 T@k_qiajp_jp@k_9T@k_qiajp*Hk]`$beha%7 r]n_jp9$bnkiaej_jp@k_*Nkkp*Ahaiajpo$l]ca%sdana± a*=ppne^qpa$l]pd%*R]hqa*Amq]ho$l]pd%± oaha_pa%*BenopKn@ab]qhp8TAhaiajp:$%7 eb$@a^qccan*Eo=pp]_da`% w ++Ej`a^qcik`ana]`kjhu]j`_na]pakqplqp ++na]`ejcTIHeopdna]`o]ba _kjpatp*Naolkjoa*Snepa$Opnejc*Bkni]p$?kqjpan9w,y(± _jp*=ppne^qpa$_kqjp%*R]hqa%%7 y ahoa w ++ejlnk`q_pekjfqopopknar]hqao Na]`anSnepanHk_gnsh9jasNa]`anSnepanHk_g$%7 nsh*=_mqenaSnepanHk_g$PeiaOl]j*BnkiOa_kj`o$.%%7 eb$_jp99jqhh% w ++l]ca`kaojkpateopuap TAhaiajpjasL]ca9jasTAhaiajp$l]ca( jasT=ppne^qpa$_kqjp(-%( jasT=ppne^qpa$l]pd(l]pd%%7 _jp@k_*Ahaiajp$L]cao%*=``$jasL]ca%7 y ahoa w ++ej_na]oa_kqjpan(oappeiaop]il ejpe9Ejp/.*L]noa$_jp*=ppne^qpa$_kqjp%*R]hqa%7 _jp*=ppne^qpa$_kqjp%*R]hqa9$''e%*PkOpnejc$%7 y _jp@k_*O]ra$beha%7 nsh*Naha]oaSnepanHk_g$%7 y y aj`nacekj y 4HEHANDLERSTORESTHENUMBEROFPAGEREQUESTSINASINGLE8-,DOCUMENT/THERDEVELOPERSCANADDTHE)&2!-% code to the pages they want included in the counter total. Internally, the file access is shared read mode. The BehaOpna]i class used behind the scenes in T@k_qiajp*Hk]`

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SUPPORTSREADINGFROMDIFFERENTTHREADS(OWEVER WRITEACCESSREQUIRESANEXCLUSIVELOCK BLOCKINGOTHERTHREADS4OACHIEVETHIS ANa]`anSnepanHk_g class monitors the threads and blocks other THREADSFROMACCESSINGTHEFILEDURINGWRITEMODE4HISISNTAVERYEFFICIENTMETHOD)NAREAL LIFE SCENARIO CONSIDERREPLACINGTHE8-,ACCESSWITHADATABASEOPERATION!FTEROBTAININGACCESSTOTHE 8-, ,).1TO8-,ISUSEDTOEITHERCREATEELEMENTSFORTHEFIRSTTIMEORADDTOTHEEXISTINGCOUNTER when the page is requested again. In the example, you want to distinguish between debug mode and production mode. You can ascertain debug mode by using the @a^qccan*Eo=pp]_da` property. In debug mode, the content OFTHE)&2!-%ISFILLEDWITHTHECOUNTERFORTHECURRENTPAGE4HE,).1STATEMENTPREPAREDATTHE beginning of the Lnk_aooNamqaop method returns either jqhh or the element containing the counter information. Figure 3-8 shows the output in debug mode. The counter does not increase for requests in debug mode. In production mode, the counter increases but no output displays.

Figure 3-8. Output of the handler in debug mode )NTHISEXAMPLE )SHOWEDAHANDLERTHATDOESNTCREATECONTENTWITHEVERYUSE4HECONCEPTS behind this are:

s $EFININGHOWANDWHERETOINVOKETHEHANDLER



s 2EMEMBERINGTHATCONCURRENTTHREADSACCESSTHECODE



s 2ECOGNIZINGTHATCREATING output is not mandatory

Example—Using IHttpHandlerFactory to Perform URL Rewriting In this example, I’ll introduce another interface. For more flexibility with creating handlers on the fly, the EDpplD]j`hanB]_pknuINTERFACEISAVAILABLE!CLOSERLOOKATTHEDEFAULTL]caD]j`hanB]_pknu SHOWSTHATITISNOTDERIVEDFROMEdpplD]j`han, but from EDpplD]j`hanB]_pknu. This class is used to process the regular *]olt pages. 9OUDONTHAVETOCREATEAFACTORY BUTITGIVESMORECONTROLOVERTHECREATIONPROCESS)TCANBE useful in more complex scenarios. First, let’s look into the interface definition: lq^he_ejpanb]_aEDpplD]j`hanB]_pknu w EDpplD]j`hanCapD]j`han$Dppl?kjpatp_kjpatp(± opnejcnamqaopPula(± opnejcqnh(± opnejcl]pdPn]joh]pa`%7 rke`Naha]oaD]j`han$EDpplD]j`hand]j`han%7 y

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NNote If you decode this using Reflector, you may see another interface named EDpplD]j`hanB]_pknu.. This provides another overload for the CapD]j`han method. You don’t need this at this stage, as you’ll only be using the EDpplD]j`hanB]_pknu. )MAGINEYOUHAVEAPAGEWITHCONTENTSUCHAS 8!9@]paPeia*Jks*PkOpnejc$I%!: 3ETTHECURRENTCULTUREBYADDINGTHECULTURE)$TOTHE52,4YPICAL52,SLOOKLIKETHIS

s dppl6++hk_]hdkop+?d]lpan,/+QnhNasnepaB]_pknuD]j`han+@ab]qhp*]olt



s dppl6++hk_]hdkop+?d]lpan,/+QnhNasnepaB]_pknuD]j`han+aj)qo+@ab]qhp*]olt



s dppl6++hk_]hdkop+?d]lpan,/+QnhNasnepaB]_pknuD]j`han+`a)`a+@ab]qhp*]olt



s dppl6++hk_]hdkop+?d]lpan,/+QnhNasnepaB]_pknuD]j`han+bn)bn+@ab]qhp*]olt

/URGOALISTOFINDAWAYTOEXTRACTTHECULTURECODESUCHAShDE DEvORhEN USv FROMTHE52, set it as the current culture of the thread, and process the page without the culture code, as shown INTHEFIRST52,,ISTING SHOWSAFACTORYTHATCREATESTHEREQUIREDINSTANCES Listing 3-12. Using a Factory to Rewrite a URL lq^he_]^opn]_p_h]ooNasnepaB]_pknuD]j`han6EDpplD]j`hanB]_pknu w lnkpa_pa`NasnepaB]_pknuD]j`han$% 6^]oa$% w y EDpplD]j`hanEDpplD]j`hanB]_pknu*CapD]j`han$Dppl?kjpatp_kjpatp(± opnejcnamqaopPula(± opnejcqnh(± opnejcl]pdPn]joh]pa`% w L]enp]ncap9CapNai]lEjbk$_kjpatp(namqaopPula(qnh(l]pdPn]joh]pa`%7 opnejcbehaj]ia9_kjpatp*Oanran*I]lL]pd$p]ncap*Benop*PkOpnejc$%%7 _kjpatp*NasnepaL]pd$qnh(qnh(p]ncap*Oa_kj`*PkOpnejc$%%7 EDpplD]j`han]llD]j`han9± L]caL]noan*Cap?kileha`L]caEjop]j_a$p]ncap*Benop*PkOpnejc$%(± behaj]ia(_kjpatp%7 napqnj]llD]j`han7 y rke`EDpplD]j`hanB]_pknu*Naha]oaD]j`han$EDpplD]j`hand]j`han% w y lnkpa_pa`]^opn]_pL]enCapNai]lEjbk$Dppl?kjpatp_kjpatp(opnejcnamqaopPula(± opnejcqnh(opnejcl]pdPn]joh]pa`%7 y lq^he__h]oo?qhpqnaNasnepaD]j`han6NasnepaB]_pknuD]j`han w

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lnkpa_pa`kranne`aL]enCapNai]lEjbk$Dppl?kjpatp_kjpatp(± opnejcnamqaopPula(± opnejcqnh(± opnejcl]pdPn]joh]pa`% w opnejcknecej]hL]pd9Dppl?kjpatp*?qnnajp*Namqaop*L]pd7 opnejcopaiL]pd9+7++At]ilha(nalh]_asepdrenpq]h`ena_pknueb]ju opnejcjasL]pd9knecej]hL]pd*Oq^opnejc$knecej]hL]pd*Ej`atKb$opaiL]pd%'± opaiL]pd*Hajcpd%7 opnejcWYoaciajpo9jasL]pd*Olhep$#+#%7 opnejcmqanuOpnejc9Dppl?kjpatp*?qnnajp*Namqaop*Qnh*Mqanu7 pnu w opnejch]jcq]caL]np9oaciajpoW,Y7 ?qhpqnaEjbk_e9jas?qhpqnaEjbk$h]jcq]caL]np%7 Ouopai*Pdna]`ejc*Pdna]`*?qnnajpPdna]`*?qnnajp?qhpqna9_e7 napqnjjasL]en$+'opaiL]pd'opnejc*Fkej$+(oaciajpo(-(± oaciajpo*Hajcpd)-%(mqanuOpnejc%7 y _]p_d$JqhhNabanaj_aAt_alpekj% w y napqnjjasL]en$knecej]hL]pd(mqanuOpnejc%7 y y The definition in web.config or IIS settings is the same as for any other handler. This means that the ASP.NET engine will accept both EDpplD]j`han and EDpplD]j`hanB]_pknu in order to obtain access to the handler object. The code is simplified for clarity. You can extend the error handling by adding code to handle THESTEMPATH EVENIFITSSETTOAVALUEOTHERTHANTHEROOTPATH4HECOREIMPLEMENTATIONISAROUND the CapD]j`han method, which returns the used handler. If resources are blocked and need to be freed or disposed of, the required code will appear in the Naha]oaD]j`han method. As shown in the example, this is not always necessary. Keep in mind that the memory consumption of the handler MIGHTBEANISSUEIFTHESERVERHASAHIGHWORKLOAD INWHICHCASERELEASINGRESOURCESCOULDHELP &IGURE SHOWSTHEBEHAVIORFORSEVERALLANGUAGES52,REWRITINGISAFLEXIBLE SEARCH ENGINE FRIENDLYMETHODOFMODIFYINGBEHAVIOR

Figure 3-9. Use URL rewriting to set the current culture of a Web application.

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4HISEXAMPLEDEMONSTRATEDAVERYBASICHANDLERFACTORY)NTHEABSTRACTBASECLASS THECapD]j`han method rewrites using Dppl?kjpatp*NasnepaL]pd4HEDEFAULTPAGEHANDLERISSUBSEQUENTLYRETRIEVEDAND returned. This is required because otherwise, the processing of all *]olt pages is remapped to the new FACTORY2EDEFININGTHEINTERNALHANDLERWITHYOUROWNONEREPLACESTHEMAPPING ASONLYONEHANDLER CANPROCESSASPECIFICREQUEST2EMAPPINGTHEDEFAULTHANDLERREQUIRESEITHERACOMPLETEIMPLEMENTATIONOFAHANDLERWITHSIMILARBEHAVIOR ORCREATINGTHEORIGINALHANDLERANDRETURNINGITUSINGAFACTORY FromTHEPERSPECTIVEOFEXTENSIBILITY THE latter is the better option.

Advanced Usage of Handlers The standardHANDLERSCOVERMOST BUTNOTALL TASKS(TTPHANDLERS can go further. In this section, I’ll DISCUSSADVANCED extensibility topics:

s !CCESSINGTHESESSIONSTATE



s $YNAMICALLYDEALINGWITHHANDLERSINTHEPIPELINE

Handlers and Session State Handlers areLOW LEVELPROGRAMMINGCONSTRUCTS4HEYARECRITICALFOROVERALLPERFORMANCEANDIF BADLYWRITTENORCONFIGURED COULDDEGRADETHESERVERSTHROUGHPUT7HILETHEREAREWAYSTODEAL with long-running threads in the handler code (as you saw in Chapter 2), it’s preferable to write HANDLERSTHATRUNASFASTASPOSSIBLE4OMAXIMIZEHANDLERSPEED -ICROSOFTREMOVEDSESSIONINFORMATIONFROMTHEDEFAULTHANDLERS4HEPREVIOUSEXAMPLESSHOWUSEFULTASKSACCOMPLISHEDWITHOUT needing session information. )FYOUDONEEDTOACCESSSESSIONSTATEINFORMATION ITISAVAILABLEBYIMPLEMENTINGONEOFTHE following two interfaces:

s ENamqena`OaooekjOp]pa



s ENa]`KjhuOaooekjOp]pa

It’s possible to obtain session information with minimal performance loss. If you only require read access to the session data, the ENa]`KjhuOaooekjOp]pa is ideal. ENamqena`OaooekjOp]paGIVESFULL ACCESSTOALLSESSIONDATA7HENADDINGEITHERINTERFACETOYOURCLASS YOULLNOTICETHAT6ISUAL3TUDIO does not attempt to implement any method bodies. Both interfaces are simply marker interfaces that modify the internal processing within the base class. Your class declaration should look like this: lq^he__h]ooPeiaD]j`hanSepdOaooekj6EDpplD]j`han(ENamqena`OaooekjOp]pa 4HESESSIONINFORMATIONISNOWPROVIDEDTOTHEDppl?kjpatpOBJECT ANDAVAILABLETHROUGHTHE _kjpatpPARAMETEROFTHEENTRYMETHOD,ISTING PASSESAVALUETHROUGHASESSIONVARIABLETOTHE handler. Listing 3-13. The Handler Implementation with Session Support lq^he__h]ooPeiaD]j`hanSepdOaooekj6EDpplD]j`han(ENa]`KjhuOaooekjOp]pa w nacekjEDpplD]j`hanIai^ano lq^he_^kkhEoNaqo]^ha w capwnapqnjpnqa7y y

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lq^he_rke`Lnk_aooNamqaop$Dppl?kjpatp_kjpatp% w @]paPeia`p7 opnejcqoaQp_9_kjpatp*Namqaop*MqanuOpnejcWqp_Y7 eb$Opnejc*EoJqhhKnAilpu$qoaQp_%""qoaQp_*Amq]ho$pnqa%% w `p9@]paPeia*Qp_Jks7 y ahoa w `p9@]paPeia*Jks7 y _kjpatp*Naolkjoa*Snepa$± Opnejc*Bkni]p$_kjpatp*OaooekjWBkni]pOpnejcY*PkOpnejc$%(± `p*PkHkjcPeiaOpnejc$%± %%7 y aj`nacekj y 4HEONLYDIFFERENCEFROMTHEPREVIOUSEXAMPLEISTHESESSIONVALUENAMEDh&ORMAT3TRINGv RETRIEVEDFROM_kjpatp*OaooekjOBJECT)NTHEAPPLICATION YOUCANSETTHATVERYVALUETOCONTROLTHE BEHAVIOROFTHEHANDLER&ORPERFORMANCEPURPOSES THEENa]`KjhuOaooekjOp]pa interface is used because only read access is required.

Accessing the Pipeline Using the Context You can use these three properties of the Dppl?kjpatpOBJECTTOFURTHERMODIFYTHEBEHAVIOROFTHE HANDLERORTORETRIEVEMOREINFORMATIONABOUTWHATISTAKINGPLACE

s _kjpatp*D]j`han



s _kjpatp*LnarekqoD]j`han



s _kjpatp*Nai]lD]j`han

5SINGTHED]j`han property YOUHAVEACCESSTOTHECURRENTHANDLEREMPLOYEDINTHECURRENT CONTEXT3INCETHECONTEXTISAVAILABLEASASTATICPROPERTY ITSEASYTOACCESSTHEHANDLERINCLASSES defined elsewhere. This also applies to the LnarekqoD]j`han property, a property that is set when the HANDLERISREMAPPED2EMAPPING a handler might occur in complex scenarios where a default hanDLERPROCESSESALLREQUESTS BUTREMAPSTOANOTHERHANDLERUNDERCERTAINCIRCUMSTANCES,ISTING  demonstrates this technique. Listing 3-14. Remapping to Another Handler lq^he__h]ooNai]lD]j`han6EDpplD]j`han w nacekjEDpplD]j`hanIai^ano lq^he_^kkhEoNaqo]^ha w capwnapqnjpnqa7y y

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lq^he_rke`Lnk_aooNamqaop$Dppl?kjpatp_kjpatp% w EDpplD]j`hannai]lD]j`han9jqhh7 ++`apanieja]jei]canamqaop]j`d]j`hasepdlner]pad]j`han eb$$L]pd*CapAtpajoekj$_kjpatp*Namqaop*Qnh*=^okhqpaL]pd%%*Amq]ho$*ljc%% w nai]lD]j`han9jasEi]caD]j`han$%7 y ahoa w ++lnk_aoo]jukpdannamqaopsepd`ab]qhpd]j`han opnejcrenpq]hL]pd9_kjpatp*Namqaop*Qnh*=^okhqpaL]pd7 opnejcbehaj]ia9Dppl?kjpatp*?qnnajp*Namqaop*L]pd7 nai]lD]j`han9L]caL]noan*Cap?kileha`L]caEjop]j_a$renpq]hL]pd(± behaj]ia(_kjpatp%7 y _kjpatp*Nai]lD]j`han$nai]lD]j`han%7 y aj`nacekj y In this code, the handler searches for *ljcEXTENSIONSANDASSIGNSPRIVATEHANDLERSTOPROCESS THEM/THERWISE YOUUSETHESTANDARDPAGEPROCESSINGNOOTHERCUSTOMCODEISINVOLVED3IMPLY call _kjpatp*Nai]lD]j`han$nai]lD]j`han% to assign to a different handler. All internal processing is redirected to the new handler from the beginning of the pipeline. As there’s noADDITIONALOVERHEAD there are no performance issues with the handler remapping.

Asynchronous Pages The processing of pages relies on just another kind of built-inHANDLER7HENPROCESSINGPAGES YOU HAVEOFTENLENGTHYOPERATIONSAGAINSTDATABASES 7EB3ERVICES OREXTERNALDATASOURCESTHATCOULD BLOCKYOURWORKERTHREADS(EREYOUMIGHTWONDERWHETHERITSPOSSIBLETOPROCESSEVENREGULAR pages asynchronously. Fortunately, the Framework already implements this for us, and there is nothing to do but set a property.

Prepare Pages for Asynchronous Operation Building asynchronous pages is simple. Begin by including an attribute in the page’s
C H A P T E R 3 N M O D U LE S A N D H A N D LE R S

That’s enough theory for now. The following examples address a common problem. It calls A7EB3ERVICEˆACURRENTEXCHANGERATESERVICETHATCONVERTSBETWEEN53AND%URO0UTTINGTHIS ONA7EB3ITEISAGOODIDEAFORASHOPTHATHASANINTERNATIONALAUDIENCE(OWEVER BLOCKINGTHE SERVERSTHREADDUETOUNPREDICTABLECALLSTOAFOREIGNSERVICEISNOSOLUTION

Figure 3-10. Synchronous vs. asynchronous page processing

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Using a Public Web Service 5SINGAPUBLIC7EB3ERVICEISBOTHCONVENIENTANDRISKY9OUHAVEAPOWERFULSERVICEAVAILABLEAND CANUSEITASTHETERMSANDCONDITIONSPERMIT(OWEVER BETWEENTHESERVICESHOSTANDYOURSERVER ISALONGDISTANCEANDMANYTHINGSCOULDGOWRONG*USTASSUMETHATTHESERVICEEXPERIENCESHIGH WORKLOAD ANDEITHERRESPONSESAREDELAYEDORTHESERVICESTOPSWORKINGCOMPLETELY"LOCKINGYOUR application’s thread could cause huge performance loss. Just to simplify first steps into the world of ASYNCHRONOUSPAGES THEFOLLOWINGEXAMPLEUSESAPUBLICSERVICETHATAPPEARSTOBEALMOSTRELIABLE 4HEREARESEVERALPUBLICSERVICESAVAILABLETOTESTSUCHANAPPLICATION!TOFTHETIMEOFPUBLISHing, the following works: dppl6++sss*sa^oanre_at*_ki+?qnnaj_u?kjranpkn*]oit.

Prepare a Project to Consume a Service The only stepREQUIREDTOCONSUMEASERVICEISTOREFERENCEIT4HEADDRESSPREVIOUSLYSHOWNISALREADY THESERVICESENDPOINTITSELF4OREFERENCETHESERVICE RIGHT CLICKTHEPROJECTANDCHOOSEh!DD7EB2EFerence” (see Figure 3-11).

Figure 3-11. Add a reference to an external Web Service.

Calling Web Services Asynchronously )FA7EB3ERVICEHAS a method named ?kjranoekjN]pa THENTHE7EB3ERVICEPROXYINCLUDESA method named ?kjranoekjN]pa=ouj_ANDANEVENTNAMED?kjranoekjN]pa?kilhapa`. You can call ?kjranoekjN]paASYNCHRONOUSLYBYREGISTERINGAHANDLERFORTHECOMPLETEDEVENTANDCALLING ?kjranoekjN]pa=ouj_ ASSHOWNIN,ISTING 

C H A P T E R 3 N M O D U LE S A N D H A N D LE R S

Listing 3-15. Calling a Web Service from an ASP.NET Page Asynchronously lq^he_l]npe]h_h]oo[@ab]qhp6Ouopai*Sa^*QE*L]ca w ?qnnaj_u?kjranpkn__7 lnkpa_pa`rke`L]ca[Hk]`$k^fa_poaj`an(Arajp=ncoa% w __9jas?qnnaj_u?kjranpkn$%7 y lnkpa_pa`rke`^pjOaj`[?he_g$k^fa_poaj`an(Arajp=ncoa% w __*?kjranoekjN]pa?kilhapa`'9jas± ?kjranoekjN]pa?kilhapa`ArajpD]j`han$__[?kjranoekjN]pa?kilhapa`%7 __*?kjranoekjN]pa=ouj_$?qnnaj_u*QO@(?qnnaj_u*AQN%7 y rke`__[?kjranoekjN]pa?kilhapa`$k^fa_poaj`an(± ?kjranoekjN]pa?kilhapa`Arajp=ncoa% w `kq^ha]ikqjp9@kq^ha*L]noa$ptp=ikqjp*Patp%7 h^hNaoqhp*Patp9$a*Naoqhp&]ikqjp%*PkOpnejc$%7 y y 4HECODEINTHEFOLLOWINGSIDEBARPRESENTSABEHINDCLASSTHATCALLSA7EB3ERVICES ?kjranoekjN]paMETHODASYNCHRONOUSLYUSINGTHEh-ETHOD!SYNCvPATTERN&UNCTIONALLY THIS ISIDENTICALTOTHEONESHOWNIN,ISTING (OWEVER INTERNALLYITISQUITEDIFFERENT!GAIN THE
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WHERE THE BEGIN-END PATTERN HAS GONE You may have read or heard about the classic Begin/End pattern used to call services asynchronously. However, when referencing a Web Service using the new style Web Project as provided in Visual Studio, the BeginMethod and EndMethod proxy methods are hidden as protected methods. Microsoft recommends using the new pattern as described in this section. However, if you like to use the old pattern, a few more steps are required. First, you can use the old style Web project (use File ° New ° Web Site instead of File ° New ° Project ° Web Project). Secondly, add the reference to the Web Service. The generated proxy will now expose the BeginMethod and EndMethod methods for all the service’s methods. Next, you have to call the =``KjLnaNaj`an?kilhapa=ouj_ method early in the page’s lifetime. For example, in Hk]` this is early enough. Register a >acej method and an Aj` method, as shown in the following code: =``KjLnaNaj`an?kilhapa=ouj_$ jas>acejArajpD]j`han$>acejIapdk`%( jasAj`ArajpD]j`han$Aj`Iapdk`% %7 The page runs through its normal processing life cycle until shortly after the LnaNaj`an event fires. Then ASP.NET calls the >acejIapdk` just registered. The method launches an asynchronous operation and returns immediately. This is the lengthy operation previously mentioned that might require more time. At this point, the thread assigned to the request returns to the thread pool. Furthermore, the method returns an E=ouj_Naoqhp that allows ASP.NET to determine when the asynchronous operation has been completed. ASP.NET then extracts a thread from the thread pool and calls your End method (Aj`Iapdk`). After this returns, it executes the remaining portion of the page’s life cycle. This might sound confusing—getting the thread back from thread pool and blocking the thread again. However, between the time >acej returns and Aj` is called, the request-processing thread is free to serve other requests. Keep in mind that the page processing usually takes only a few milliseconds. The time-consuming operation in the asynchronous handler might run for seconds. The process of freeing the thread pool thread for this time allows ASP.NET to process hundreds, if not thousands, of regular pages on this very same thread. However, until Aj` is called, the rendering of the current asynchronous page is delayed. This is the same as in the previous example. It improves the situation not only for one user, but also for all users. In the sample code, you might look for the E=ouj_Naoqhp implementation. Instead of implementing our own version, you take one that the Framework implements for us. The complete code of such an example would look like the following: lq^he_l]npe]h_h]oo[@ab]qhp6Ouopai*Sa^*QE*L]ca w ?qnnaj_u?kjranpkn__7 lnkpa_pa`rke`L]ca[Hk]`$k^fa_poaj`an(Arajp=ncoa% w y E=ouj_Naoqhp>acej?kjranoekj$k^fa_poaj`an(Arajp=ncoa( =ouj_?]hh^]_g_^(k^fa_pop]pa% w __9jas?qnnaj_u?kjranpkn$%7 napqnj__*>acej?kjranoekjN]pa$?qnnaj_u*QO@(?qnnaj_u*AQN(_^(op]pa%7 y

C H A P T E R 3 N M O D U LE S A N D H A N D LE R S

rke`Aj`?kjranoekj$E=ouj_Naoqhp]n% w `kq^hanaoqhp9__*Aj`?kjranoekjN]pa$]n%7 `kq^ha]ikqjp9@kq^ha*L]noa$ptp=ikqjp*Patp%7 h^hNaoqhp*Patp9$naoqhp&]ikqjp%*PkOpnejc$%7 y

lnkpa_pa`rke`^pjOaj`[?he_g$k^fa_poaj`an(Arajp=ncoa% w =``KjLnaNaj`an?kilhapa=ouj_$ jas>acejArajpD]j`han$>acej?kjranoekj%( jasAj`ArajpD]j`han$Aj`?kjranoekj%%7 y y Here the asynchronous methods are registered with the Button’s click event. >acej?kjranoekjN]pa and Aj`?kjranoekjN]pa are the methods used to invoke the service and get the result back.

Configuration and Deployment 4OCREATEAHANDLER YOUCHOSEh#LASS,IBRARYvASTHEPROJECTTEMPLATE REMOVED the default class CREATEDBYTHETEMPLATE ANDADDEDANOBJECTOFTYPEh!30.%4(ANDLERv.OWTHATYOUHAVE implemented the handler, you can compile it into an assembly loaded by ASP.NET at runtime (see Figure 3-12). As long as the handler remains in the web application, this is simple. No special action ISREQUIRED9OULLPROBABLYWANTTOIMPLEMENTSEVERALHANDLERSANDKEEPTHEMINDIFFERENTASSEMblies for easy reuse. Simply reference the assemblies in your web project.

Figure 3-12. Add a handler to the current project

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Configuring Default Web Server and Development Environment To test the handler, you’ll need to configure the settings in web.config. Place the appropriate settings in the 8ouopai*sa^: section: 8dpplD]j`hano: 8]``ran^9CAPl]pd9&*ljcpula9=lnaoo*DpplD]j`han*Ei]caD]j`han+: 8+dpplD]j`hano: )NCASEYOUHAVEASIMILARHANDLERDEFINITIONINTHEUPSIDECONFIGURATIONPATHYOUMIGHTCONsider using either 8naikra+: or 8_ha]n+:TAGSTOOVERWRITETHEVALUESPROPERLY 4HESETTINGSFORTHEDEVELOPMENTENVIRONMENTALSOAPPLYTO))3 ))3 AND))3INCLASSICMODE 4HEREARESEVERALADVANTAGESˆASEXPLAINEDIN#HAPTERˆTORUNNINGTHE))3INTEGRATEDPIPELINE HOWEVER WHICHINVOLVESTHEDIFFERENTSETTINGS shown in Table 3-12. Table 3-12. Options of the httpHandler Settings

Attribute

Typical Values

Description

ran^

'%4 0/34

4HEHANDLERRESPONDSTOTHE(440VERBSONLY

l]pd

full path or wildcards

The path that defines the requests the handlers responds to.

pula

class, assembly

Type information of the handler’s definition.

Configuring IIS7 Settings In the main (web) project, add a reference to this project. If the namespace of the external project is =lnaoo*DppD]j`han*Ei]caD]j`han, the following addition to web.config will be required: 8ouopai*sa^Oanran: 8d]j`hano: 8]``j]ia9Ei]caD]j`hanl]pd9&*ljcran^9CAP pula9=lnaoo*DpplD]j`han*Ei]caD]j`hannaokqn_aPula9Beha namqena=__aoo9Na]`lna?kj`epekj9ejpacn]pa`Ik`a+: 8+d]j`hano: 8+ouopai*sa^Oanran: Compile both the project containing the handler and the web project. Add the mapping in )NTERNET)NFORMATION3ERVICES-ANAGER ASSHOWNBEFORE4HEMAPPINGWILLNOWFUNCTIONPERFECTLY FORBOTHTHEDEVELOPMENTENVIRONMENTANDDIRECTUSAGEFROMTHELOCAL))3SEE4ABLE   Table 3-13. Handler Settings for IIS7 Integrated Mode

Attribute

Typical Values

Description

ran^

'%4 0/34

The handler responds to the HTTP VERBSONLY/THERVERBSARE$%"5' AND(%!$

l]pd

full path or wildcards

The path that defines the requests the handlers respond to.

naokqn_aPula

File

Expect that the file exists.

o_nelpLnk_aookn

a path

0ATHTOTHEENGINE$,, THATHANDLES the request.

namqena=__aoo

3CRIPT %XECUTE .ONE 2EAD 7RITE

2EQUIREDSETTINGSFORRESOURCEACCESS

C H A P T E R 3 N M O D U LE S A N D H A N D LE R S

Attribute

Typical Values

Description

naokqn_aPula

$IRECTORY %ITHER &ILE 5NSPECIFIED

The type of the resource the handler ISMAPPEDTO4HEDEFAULTVALUEIS 5NSPECIFIED

lna?kj`epekj

See following list

Conditions that must be fulfilled to ACTIVATETHEHANDLER)FTHEREQUESTFAILS AN(440ERRORhPRECONDITIONFAILEDv is sent to the client.

]hhksL]pdEjbk

true,false

Specifies whether the handler processes full path information. If set to false, the handler processes the file information part of a path only.

ik`qhao

Names

/PTIONALCOMMASEPARATEDLISTOF modules the extension is mapped to. By default, handler settings map to -ANAGED0IPELINE(ANDLER

pula

class, assembly

The type name of the handler.

TypicalVALUESFORlna?kj`epekj are these:

s ^epjaoo/., ^epjaoo20!CTIVATE BITOR BITMODERESPECTIVELY



s nqjpeiaRanoekj-*-, nqjpeiaRanoekj.*,4HEREQUIREDRUNTIMEONTHESERVER



s _h]ooe_Ik`a, ejpacn]pa`Ik`a-ODETHAT))3ISRUNNINGIN



s i]j]ca`D]j`han2EQUIRESTHEHANDLERTOBEWRITTENINMANAGEDCODE

Configure via IIS Management Console The settings in web.configREQUIREDBY))3INTEGRATEDMODECANBEALTEREDVIATHE))3-ANAGEMENT Console. The settings correspond directly. Altering web.config will result in an immediate change to THE-ANAGEMENT#ONSOLESETTINGS ANDVICEVERSA4OCONFIGUREUSINGTHE))3-ANAGEMENT#ONSOLE 1. /PEN)NTERNET)NFORMATION3ERVICE-ANAGER 2. /PENTHEWEBYOUWANTTOCHANGE 3. )NTHE))3SECTION DOUBLE CLICKONTHE(ANDLER-APPINGS 4. #LICKON!DD-ANAGED(ANDLERINTHETASKLISTTOTHERIGHT 5. %NTERTHESEVALUESINTHEDIALOG,EAVETHEDIALOGBYCLICKING/+ THEN a. 4HE2EQUESTPATH TIME b. Choose the handler from the drop-down list. The handler will appear in the list, as long as you’re in the right web and the project compiles. c. 'IVETHEHANDLERANAPPROPRIATENAME d. #LICKON2EQUEST2ESTRICTIONS e. /PENTHE6ERBSTAB f. #LICKONONEOFTHEFOLLOWINGVERBSANDENTERTHEVALUEh'%4v 6. ,EAVETHEMAINDIALOGBYCLICKING/+

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Configure Using Generic Handlers The final optionISNOTACONFIGURATIONOPTION BUTAWAYOFINVOKINGHANDLERSWITHOUTCONFIGURING them in web.config. By default, ASP.NET defines handlers using the extension *]odt. Therefore, PLACINGTHECODEFORAHANDLERINAFILEUSINGTHEFOLLOWINGDECLARATIVEFORMISSUFFICIENTTOGETIT working. There is no further need for web.config!NADVANTAGEOFTHISISTHATYOUWONTNEEDTODISTINGUISHBETWEENTHESETTINGSFOR))3INTEGRATEDMODEANDOTHER7EB3ERVERS NORWILLYOUNEEDTO maintain settings in the web.config regarding handlers. #REATINGSUCHAHANDLERINVOLVESTWOSTEPS 1. For each handler required, crea