1.C# 3.0: The Complete ReferencePresented By: Oronno - "The ONE"www.the1.co.nr

2. About the Author Herbert Schildt is a leading authority on C#, C++, C, and Java. His programming books have sold more than 3.5 million copies worldwide and have been translated into all major foreign languages. He is the author of numerous bestsellers, including Java: The Complete Reference, C++: The Complete Reference, C: The Complete Reference, and C#: A Beginners Guide. Although interested in all facets of computing, his primary focus is computer languages, including compilers, interpreters, and robotic control languages. He also has an active interest in the standardization of languages. Schildt holds both graduate and undergraduate degrees from the University of Illinois. He can be reached at his consulting office at (217) 586-4683. His web site is www.HerbSchildt.com.About the Technical Editor Michael Howard (Austin, Texas) is a principal security program manager on the Trustworthy Computing (TwC) Groups Security Engineering team at Microsoft, where he is responsible for managing secure design, programming, and testing techniques across the company. Howard is an architect of the Security Development Lifecycle (SDL), a process for improving the security of Microsofts software. Howard speaks regularly on the topic of securing code for Microsoft and at conferences worldwide. He regularly publishes articles on security design and is the co-author of six security books, including the award-winning Writing Secure Code, 19 Deadly Sins of Software Security, The Security Development Lifecycle, and his most recent release, Writing Secure Code for Windows Vista. 3. C# 3.0: The Complete Reference Herbert SchildtNew York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto 4. Copyright 2009 by The McGraw-Hill Companies. All rights reserved. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher. ISBN: 978-0-07-159842-2 MHID: 0-07-159842-6 The material in this eBook also appears in the print version of this title: ISBN: 978-0-07-158841-6, MHID: 0-07-158841-8. All trademarks are trademarks of their respective owners. Rather than put a trademark symbol after every occurrence of a trademarked name, we use names in an editorial fashion only, and to the benefit of the trademark owner, with no intention of infringement of the trademark. Where such designations appear in this book, they have been printed with initial caps. McGraw-Hill eBooks are available at special quantity discounts to use as premiums and sales promotions, or for use in corporate training programs. To contact a representative please visit the Contact Us page at www.mhprofessional.com. Information has been obtained by McGraw-Hill from sources believed to be reliable. However, because of the possibility of human or mechanical error by our sources, McGraw-Hill, or others, McGraw-Hill does not guarantee the accuracy, adequacy, or completeness of any information and is not responsible for any errors or omissions or the results obtained from the use of such information.TERMS OF USE This is a copyrighted work and The McGraw-Hill Companies, Inc. (McGraw-Hill) and its licensors reserve all rights in and to the work. Use of this work is subject to these terms. Except as permitted under the Copyright Act of 1976 and the right to store and retrieve one copy of the work, you may not decompile, disassemble, reverse engineer, reproduce, modify, create derivative works based upon, transmit, distribute, disseminate, sell, publish or sublicense the work or any part of it without McGraw-Hills prior consent. You may use the work for your own noncommercial and personal use; any other use of the work is strictly prohibited. Your right to use the work may be terminated if you fail to comply with these terms. THE WORK IS PROVIDED AS IS. McGRAW-HILL AND ITS LICENSORS MAKE NO GUARANTEES OR WARRANTIES AS TO THE ACCURACY, ADEQUACY OR COMPLETENESS OF OR RESULTS TO BE OBTAINED FROM USING THE WORK, INCLUDING ANY INFORMATION THAT CAN BE ACCESSED THROUGH THE WORK VIA HYPERLINK OR OTHERWISE, AND EXPRESSLY DISCLAIM ANY WARRANTY, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. McGraw-Hill and its licensors do not warrant or guarantee that the functions contained in the work will meet your requirements or that its operation will be uninterrupted or error free. Neither McGraw-Hill nor its licensors shall be liable to you or anyone else for any inaccuracy, error or omission, regardless of cause, in the work or for any damages resulting therefrom. McGraw-Hill has no responsibility for the content of any information accessed through the work. Under no circumstances shall McGraw-Hill and/or its licensors be liable for any indirect, incidental, special, punitive, consequential or similar damages that result from the use of or inability to use the work, even if any of them has been advised of the possibility of such damages. This limitation of liability shall apply to any claim or cause whatsoever whether such claim or cause arises in contract, tort or otherwise. 5. Contents at a Glance Part I The C# Language 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20The Creation of C# . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . An Overview of C# . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Types, Literals, and Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Program Control Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introducing Classes and Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arrays and Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Closer Look at Methods and Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Operator Overloading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Indexers and Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interfaces, Structures, and Enumerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exception Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Delegates, Events, and Lambda Expressions . . . . . . . . . . . . . . . . . . . . . . . . . Namespaces, the Preprocessor, and Assemblies . . . . . . . . . . . . . . . . . . . . . . Runtime Type ID, Reection, and Attributes . . . . . . . . . . . . . . . . . . . . . . . . Generics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LINQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unsafe Code, Pointers, Nullable Types, and Miscellaneous Topics . . . . .3 11 35 63 85 109 137 165 213 245 269 311 337 363 399 437 459 495 545 585Part II Exploring the C# Library 21 22 23 24 25 26 AExploring the System Namespace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Strings and Formatting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multithreaded Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Collections, Enumerators, and Iterators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Networking Through the Internet Using System.Net . . . . . . . . . . . . . . . . . Use System.Windows.Forms to Create Form-Based Windows Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Documentation Comment Quick Reference . . . . . . . . . . . . . . . . . . . . . . . . .615 663 703 749 821Index871...........................................................847 867v 6. This page intentionally left blank 7. Contents Special Thanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiiiPart I The C# Language 1The Creation of C# . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C#s Family Tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C: The Beginning of the Modern Age of Programming . . . . . . . . . . . The Creation of OOP and C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Internet and Java Emerge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Creation of C# . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Evolution of C# . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . How C# Relates to the .NET Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What Is the .NET Framework? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . How the Common Language Runtime Works . . . . . . . . . . . . . . . . . . . . . . . . . Managed vs. Unmanaged Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Common Language Specication . . . . . . . . . . . . . . . . . . . . . . . . . .3 3 3 4 4 5 7 7 8 8 9 92An Overview of C# . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Object-Oriented Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polymorphism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A First Simple Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using csc.exe, the C# Command-Line Compiler . . . . . . . . . . . . . . . . . Using the Visual Studio IDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The First Sample Program, Line by Line . . . . . . . . . . . . . . . . . . . . . . . . Handling Syntax Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Small Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Second Simple Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Another Data Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Two Control Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The if Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The for Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Code Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Semicolons, Positioning, and Indentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . The C# Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Identiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The .NET Framework Class Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 11 12 12 13 13 14 15 19 22 22 23 25 26 27 28 29 31 32 33 34vii 8. viiiC# 3.0: The Complete Reference3Data Types, Literals, and Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Why Data Types Are Important . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C#s Value Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Integers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Floating-Point Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The decimal Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The bool Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Some Output Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Literals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hexadecimal Literals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Character Escape Sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . String Literals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Closer Look at Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Initializing a Variable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dynamic Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Implicitly Typed Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Scope and Lifetime of Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Type Conversion and Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Automatic Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Casting Incompatible Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Type Conversion in Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Casts in Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 35 35 36 38 40 41 42 43 46 47 47 48 49 50 50 51 52 55 55 56 59 604Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arithmetic Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Increment and Decrement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Relational and Logical Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Short-Circuit Logical Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Assignment Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Compound Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Bitwise Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Bitwise AND, OR, XOR, and NOT Operators . . . . . . . . . . . . . . . The Shift Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bitwise Compound Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The ? Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spacing and Parentheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Operator Precedence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63 63 64 67 70 71 72 73 73 79 81 82 83 845Program Control Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The if Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nested ifs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The if-else-if Ladder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The switch Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nested switch Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The for Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Some Variations on the for Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85 85 86 87 88 92 92 94 9. ContentsThe while Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The do-while Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The foreach Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using break to Exit a Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using continue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . return . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The goto . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99 101 102 102 104 105 1056Introducing Classes and Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Class Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The General Form of a Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dene a Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . How Objects Are Created . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reference Variables and Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Add a Method to the Building Class . . . . . . . . . . . . . . . . . . . . . . . . . . . Return from a Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Return a Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Add a Parameterized Method to Building . . . . . . . . . . . . . . . . . . . . . . Avoiding Unreachable Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parameterized Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Add a Constructor to the Building Class . . . . . . . . . . . . . . . . . . . . . . . The new Operator Revisited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using new with Value Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Garbage Collection and Destructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Destructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The this Keyword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109 109 109 110 114 115 116 117 119 120 122 125 126 126 128 129 130 130 131 131 1337Arrays and Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . One-Dimensional Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multidimensional Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Two-Dimensional Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arrays of Three or More Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . Initializing Multidimensional Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . Jagged Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Assigning Array References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using the Length Property . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Length with Jagged Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Implicitly Typed Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The foreach Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Constructing Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Operating on Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arrays of Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137 137 137 141 141 142 143 144 146 148 150 151 152 156 156 157 160ix 10. xC# 3.0: The Complete ReferenceStrings Are Immutable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Strings Can Be Used in switch Statements . . . . . . . . . . . . . . . . . . . . . .161 1628A Closer Look at Methods and Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Controlling Access to Class Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C#s Access Modiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applying Public and Private Access . . . . . . . . . . . . . . . . . . . . . . . . . . . Controlling Access: A Case Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pass References to Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . How Arguments Are Passed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use ref and out Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use ref . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use ref and out on References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use a Variable Number of Arguments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Return Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Return an Array . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Method Overloading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overload Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Invoke an Overloaded Constructor Through this . . . . . . . . . . . . . . . . Object Initializers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Main( ) Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Return Values from Main( ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pass Arguments to Main( ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Recursion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Understanding static . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Static Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Static Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .165 165 165 167 168 172 174 176 177 178 181 182 185 187 188 194 197 199 200 200 200 202 205 210 2119Operator Overloading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Operator Overloading Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overloading Binary Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overloading Unary Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Handling Operations on C# Built-in Types . . . . . . . . . . . . . . . . . . . . . . . . . . . Overloading the Relational Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overloading true and false . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overloading the Logical Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Simple Approach to Overloading the Logical Operators . . . . . . . . Enabling the Short-Circuit Operators . . . . . . . . . . . . . . . . . . . . . . . . . . Conversion Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Operator Overloading Tips and Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . Another Example of Operator Overloading . . . . . . . . . . . . . . . . . . . . . . . . . . .213 213 214 216 220 224 226 229 229 231 235 239 24010Indexers and Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Indexers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Creating One-Dimensional Indexers . . . . . . . . . . . . . . . . . . . . . . . . . . . Indexers Can Be Overloaded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .245 245 245 249 11. ContentsIndexers Do Not Require an Underlying Array . . . . . . . . . . . . . . . . . . Multidimensional Indexers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Auto-Implemented Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use Object Initializers with Properties . . . . . . . . . . . . . . . . . . . . . . . . . Property Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use Access Modiers with Accessors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Indexers and Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .251 252 254 259 260 261 261 26411Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inheritance Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Member Access and Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Protected Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Constructors and Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Calling Base Class Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inheritance and Name Hiding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using base to Access a Hidden Name . . . . . . . . . . . . . . . . . . . . . . . . . . Creating a Multilevel Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . When Are Constructors Called? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Base Class References and Derived Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . Virtual Methods and Overriding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Why Overridden Methods? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applying Virtual Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Abstract Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using sealed to Prevent Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The object Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Boxing and Unboxing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Is object a Universal Data Type? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .269 269 272 275 276 278 282 283 285 288 289 294 297 298 301 305 305 307 30912Interfaces, Structures, and Enumerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Implementing Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Interface References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interface Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interface Indexers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interfaces Can Be Inherited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Name Hiding with Interface Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Explicit Implementations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Choosing Between an Interface and an Abstract Class . . . . . . . . . . . . . . . . . . The .NET Standard Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Why Structures? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Enumerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Initialize an Enumeration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specify the Underlying Type of an Enumeration . . . . . . . . . . . . . . . . Use Enumerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .311 311 312 316 318 320 322 323 323 326 326 326 330 332 333 334 334xi 12. xiiC# 3.0: The Complete Reference13Exception Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The System.Exception Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exception Handling Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using try and catch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Simple Exception Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Second Exception Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Consequences of an Uncaught Exception . . . . . . . . . . . . . . . . . . . . . . . . . Exceptions Let You Handle Errors Gracefully . . . . . . . . . . . . . . . . . . . . . . . . . Using Multiple catch Clauses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Catching All Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nesting try Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Throwing an Exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rethrowing an Exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using nally . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Closer Look at the Exception Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commonly Used Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Deriving Exception Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Catching Derived Class Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using checked and unchecked . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .337 337 338 338 338 340 341 343 344 345 346 347 348 349 351 352 354 358 36014Using I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C#s I/O Is Built Upon Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Byte Streams and Character Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . The Predened Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Stream Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Stream Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Byte Stream Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Character Stream Wrapper Classes . . . . . . . . . . . . . . . . . . . . . . . . Binary Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Console I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reading Console Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using ReadKey( ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Writing Console Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FileStream and Byte-Oriented File I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Opening and Closing a File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reading Bytes from a FileStream . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Writing to a File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using FileStream to Copy a File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Character-Based File I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using StreamWriter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using a StreamReader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Redirecting the Standard Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reading and Writing Binary Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BinaryWriter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BinaryReader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Demonstrating Binary I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .363 363 363 363 364 364 365 365 367 367 367 369 371 371 372 374 375 376 378 378 380 381 383 383 384 386 13. ContentsRandom Access Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using MemoryStream . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using StringReader and StringWriter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Converting Numeric Strings to Their Internal Representation . . . . . . . . . . .390 392 394 39615Delegates, Events, and Lambda Expressions . . . . . . . . . . . . . . . . . . . . . . . . . Delegates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Delegate Method Group Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . Using Instance Methods as Delegates . . . . . . . . . . . . . . . . . . . . . . . . . . Multicasting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Covariance and Contravariance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . System.Delegate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Why Delegates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anonymous Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anonymous Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pass Arguments to an Anonymous Method . . . . . . . . . . . . . . . . . . . . . Return a Value from an Anonymous Method . . . . . . . . . . . . . . . . . . . Use Outer Variables with Anonymous Methods . . . . . . . . . . . . . . . . . Lambda Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Lambda Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Expression Lambdas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Statement Lambdas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Multicast Event Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Instance Methods vs. Static Methods as Event Handlers . . . . . . . . . . Using Event Accessors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Miscellaneous Event Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use Anonymous Methods and Lambda Expressions with Events . . . . . . . . .NET Event Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use EventHandler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applying Events: A Case Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .399 399 402 402 404 406 408 408 408 409 410 410 412 413 413 414 416 419 421 422 424 429 429 430 432 43316Namespaces, the Preprocessor, and Assemblies . . . . . . . . . . . . . . . . . . . . . . Namespaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Declaring a Namespace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Namespaces Prevent Name Conicts . . . . . . . . . . . . . . . . . . . . . . . . . . using . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Second Form of using . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Namespaces Are Additive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Namespaces Can Be Nested . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Global Namespace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using the :: Namespace Alias Qualier . . . . . . . . . . . . . . . . . . . . . . . . The Preprocessor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . #dene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . #if and #endif . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . #else and #elif . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . #undef . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .437 437 438 440 441 443 444 446 447 447 451 452 452 454 455xiii 14. xivC# 3.0: The Complete Reference#error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . #warning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . #line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . #region and #endregion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . #pragma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Assemblies and the internal Access Modier . . . . . . . . . . . . . . . . . . . . . . . . . The internal Access Modier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .456 456 456 456 457 457 45817Runtime Type ID, Reection, and Attributes . . . . . . . . . . . . . . . . . . . . . . . . Runtime Type Identication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Testing a Type with is . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using as . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using typeof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Reection Core: System.Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Reection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Obtaining Information About Methods . . . . . . . . . . . . . . . . . . . . . . . . Calling Methods Using Reection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Obtaining a Types Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Obtaining Types from Assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fully Automating Type Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Attribute Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Positional vs. Named Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Three Built-in Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AttributeUsage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Conditional Attribute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Obsolete Attribute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .459 459 459 460 462 463 463 465 465 469 471 475 481 483 483 487 491 491 491 49318Generics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What Are Generics? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Simple Generics Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Generic Types Differ Based on Their Type Arguments . . . . . . . . . . . . How Generics Improve Type Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . A Generic Class with Two Type Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . The General Form of a Generic Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Constrained Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using a Base Class Constraint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using an Interface Constraint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using the new( ) Constructor Constraint . . . . . . . . . . . . . . . . . . . . . . . The Reference Type and Value Type Constraints . . . . . . . . . . . . . . . . Using a Constraint to Establish a Relationship Between Two Type Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Multiple Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Creating a Default Value of a Type Parameter . . . . . . . . . . . . . . . . . . . . . . . . . Generic Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Creating a Generic Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .495 495 496 499 499 502 503 503 504 512 516 517 520 521 522 523 524 15. ContentsUsing Explicit Type Arguments to Call a Generic Method . . . . . . . . Using a Constraint with a Generic Method . . . . . . . . . . . . . . . . . . . . . Generic Delegates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Generic Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparing Instances of a Type Parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . Generic Class Hierarchies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using a Generic Base Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Generic Derived Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overriding Virtual Methods in a Generic Class . . . . . . . . . . . . . . . . . . . . . . . . Overloading Methods That Use Type Parameters . . . . . . . . . . . . . . . . . . . . . How Generic Types Are Instantiated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Some Generic Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Final Thoughts on Generics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .527 527 527 530 534 537 537 539 540 542 543 544 54419LINQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What Is LINQ? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LINQ Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Simple Query . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Query Can Be Executed More Than Once . . . . . . . . . . . . . . . . . . . . How the Data Types in a Query Relate . . . . . . . . . . . . . . . . . . . . . . . . . The General Form of a Query . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Filter Values with where . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sort Results with orderby . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Closer Look at select . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use Nested from Clauses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Group Results with group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use into to Create a Continuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use let to Create a Variable in a Query . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Join Two Sequences with join . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anonymous Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Create a Group Join . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Query Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Basic Query Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Create Queries by Using the Query Methods . . . . . . . . . . . . . . . . . . . Query Syntax vs. Query Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . More Query-Related Extension Methods . . . . . . . . . . . . . . . . . . . . . . . Deferred vs. Immediate Query Execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . Expression Trees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Extension Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .545 545 546 546 548 549 550 551 552 556 560 561 563 565 566 569 571 574 574 575 577 577 580 581 58220Unsafe Code, Pointers, Nullable Types, and Miscellaneous Topics . . . . . Unsafe Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pointer Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using unsafe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using xed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Accessing Structure Members Through a Pointer . . . . . . . . . . . . . . . .585 585 586 587 588 589xv 16. xviC# 3.0: The Complete ReferencePointer Arithmetic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pointer Comparisons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pointers and Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pointers and Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multiple Indirection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arrays of Pointers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . stackalloc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Creating Fixed-Size Buffers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nullable Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nullable Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nullable Objects in Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The ?? Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nullable Objects and the Relational and Logical Operators . . . . . . . Partial Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Partial Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Friend Assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Miscellaneous Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . readonly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . const and volatile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The using Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . extern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .589 591 591 593 594 595 596 596 598 598 600 601 602 603 604 605 605 605 606 607 607 608Part II Exploring the C# Library 21Exploring the System Namespace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Members of System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Math Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The .NET Structures Corresponding to the Built-in Value Types . . . . . . . . . The Integer Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Floating-Point Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Decimal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Char . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Boolean Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Array Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sorting and Searching Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reversing an Array . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Copying an Array . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using a Predicate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using an Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BitConverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Generating Random Numbers with Random . . . . . . . . . . . . . . . . . . . . . . . . . Memory Management and the GC Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Object . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The IComparable and IComparable Interfaces . . . . . . . . . . . . . . . . . . . . . The IEquatable Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .615 615 617 623 623 626 630 634 640 641 648 650 651 652 653 654 656 657 659 659 660 17. ContentsThe IConvertible Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The ICloneable Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IFormatProvider and IFormattable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .660 660 66222Strings and Formatting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Strings in C# . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The String Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The String Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The String Field, Indexer, and Property . . . . . . . . . . . . . . . . . . . . . . . . The String Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The String Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Padding and Trimming Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inserting, Removing, and Replacing . . . . . . . . . . . . . . . . . . . . . . . . . . . Changing Case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using the Substring( ) Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The String Extension Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Formatting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Formatting Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Numeric Format Speciers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Understanding Argument Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . Using String.Format( ) and ToString( ) to Format Data . . . . . . . . . . . . . . . . . Using String.Format( ) to Format Values . . . . . . . . . . . . . . . . . . . . . . . Using ToString( ) to Format Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Creating a Custom Numeric Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Custom Format Placeholder Characters . . . . . . . . . . . . . . . . . . . . Formatting Date and Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Creating a Custom Date and Time Format . . . . . . . . . . . . . . . . . . . . . . Formatting Enumerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .663 663 664 664 665 665 665 681 682 683 684 684 684 685 686 687 688 688 691 692 692 695 698 70023Multithreaded Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multithreading Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Thread Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Creating and Starting a Thread . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Some Simple Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Creating Multiple Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Determining When a Thread Ends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Passing an Argument to a Thread . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The IsBackground Property . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thread Priorities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . An Alternative Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Monitor Class and lock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thread Communication Using Wait( ), Pulse( ), and PulseAll( ) . . . . . . . . . An Example That Uses Wait( ) and Pulse( ) . . . . . . . . . . . . . . . . . . . . . Deadlock and Race Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using MethodImplAttribute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using a Mutex and a Semaphore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .703 703 704 704 707 708 710 713 715 715 717 721 723 723 724 727 728 730xvii 18. xviiiC# 3.0: The Complete ReferenceThe Mutex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Semaphore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Interlocked Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Terminating a Thread . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . An Abort( ) Alternative . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Canceling Abort( ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Suspending and Resuming a Thread . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Determining a Threads State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using the Main Thread . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multithreading Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Starting a Separate Task . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .730 734 737 739 741 742 743 745 745 746 747 74724Collections, Enumerators, and Iterators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Collections Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Non-Generic Collections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Non-Generic Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The DictionaryEntry Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Non-Generic Collection Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . Storing Bits with BitArray . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Specialized Collections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Generic Collections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Generic Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The KeyValuePair Structure . . . . . . . . . . . . . . . . . . . . . . . . . The Generic Collection Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Storing User-Dened Classes in Collections . . . . . . . . . . . . . . . . . . . . . . . . . . Implementing IComparable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Implementing IComparable for Non-Generic Collections . . . . . . . . . Implementing IComparable for Generic Collections . . . . . . . . . . Using an IComparer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using a Non-Generic IComparer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using a Generic IComparer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Accessing a Collection via an Enumerator . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using an Enumerator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using the IDictionaryEnumerator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Implementing IEnumerable and IEnumerator . . . . . . . . . . . . . . . . . . . . . . . . Using Iterators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stopping an Iterator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Multiple yield Directives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Creating a Named Iterator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Creating a Generic Iterator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Collection Initializers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .749 749 750 751 755 755 771 774 774 775 778 779 799 801 802 803 805 805 806 808 808 809 811 813 815 815 816 818 81925Networking Through the Internet Using System.Net . . . . . . . . . . . . . . . . . The System.Net Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Uniform Resource Identiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .821 821 823 19. ContentsInternet Access Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . WebRequest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . WebResponse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . HttpWebRequest and HttpWebResponse . . . . . . . . . . . . . . . . . . . . . . . A Simple First Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Handling Network Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exceptions Generated by Create( ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exceptions Generated by GetReponse( ) . . . . . . . . . . . . . . . . . . . . . . . . Exceptions Generated by GetResponseStream( ) . . . . . . . . . . . . . . . . . Using Exception Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Uri Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Accessing Additional HTTP Response Information . . . . . . . . . . . . . . . . . . . . Accessing the Header . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Accessing Cookies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using the LastModied Property . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MiniCrawler: A Case Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using WebClient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26A823 824 826 826 827 830 830 830 831 831 833 834 834 836 838 839 842Use System.Windows.Forms to Create Form-Based Windows Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Brief History of Windows Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . Two Ways to Write a Form-Based Windows Application . . . . . . . . . . . . . . . How Windows Interacts with the User . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Windows Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Form Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Skeletal Form-Based Windows Program . . . . . . . . . . . . . . . . . . . . . . . . . . . Compiling the Windows Skeleton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Adding a Button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Button Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Adding a Button to a Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Simple Button Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Handling Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . An Alternative Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using a Message Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Adding a Menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Creating a Traditional-Style Main Menu . . . . . . . . . . . . . . . . . . . . . . . Creating a New-Style Menu with MenuStrip . . . . . . . . . . . . . . . . . . .847 847 848 848 849 849 849 851 852 852 852 853 853 856 856 859 859 863Documentation Comment Quick Reference . . . . . . . . . . . . . . . . . . . . . . . . . The XML Comment Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Compiling Documentation Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . An XML Documentation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .867 867 868 869...........................................................871Indexxix 20. This page intentionally left blank 21. Special ThanksSpecial thanks go to Michael Howard for his excellent technical edit of this book. His expertise, insights, suggestions, and advice were of great value.xxi 22. This page intentionally left blank 23. PrefaceWe programmers are a demanding bunch, always looking for ways to improve the performance, efficiency, and portability of our programs. We also demand much from the tools we use, especially when it comes to programming languages. There are many programming languages, but only a few are great. A great programming language must be powerful, yet flexible. Its syntax must be terse, but clear. It must facilitate the creation of correct code while not getting in our way. It must support state-of-the-art features, but not trendy dead ends. Finally, a great programming language must have one more, almost intangible quality: It must feel right when we use it. C# is such a language. Created by Microsoft to support its .NET Framework, C# builds on a rich programming heritage. Its chief architect was long-time programming guru Anders Hejlsberg. C# is directly descended from two of the worlds most successful computer languages: C and C++. From C, it derives its syntax, many of its keywords, and its operators. It builds upon and improves the object model defined by C++. C# is also closely related to another very successful language: Java. Sharing a common ancestry, but differing in many important ways, C# and Java are more like cousins. Both support distributed programming and both use intermediate code to achieve safety and portability, but the details differ. They both also provide a significant amount of runtime error checking, security, and managed execution, but again, the details differ. However, unlike Java, C# also gives you access to pointersa feature supported by C++. Thus, C# combines the raw power of C++ with the type safety of Java. Furthermore, the trade-offs between power and safety are carefully balanced and are nearly transparent. Throughout the history of computing, programming languages have evolved to accommodate changes in the computing environment, advances in computer language theory, and new ways of thinking about and approaching the job of programming. C# is no exception. In the ongoing process of refinement, adaptation, and innovation, C# has demonstrated its ability to respond rapidly to the changing needs of the programmer. This fact is testified to by the many new features added to C# since its initial 1.0 release in 2000. Consider the first major revision, C# 2.0. It added several features that made it easier for programmers to write more resilient, reliable, and nimble code. Without question, the most important 2.0 addition was generics. Through the use of generics, it became possible to create type-safe, reusable code in C#. Thus, the addition of generics fundamentally expanded the power and scope of the language. Now consider the second major revision, C# 3.0. This is the latest version of C# and is the version described in this book. It is not an exaggeration to say that C# 3.0 has added features that have redefined the very core of C#, raising the bar in computer language development in the process. Of its many innovative features, two stand out: LINQ and lambda expressions. LINQ, which stands for Language Integrated Query, enables you to create database-style queries by using elements of the C# language. Lambda expressions implement a functionalstyle syntax that uses the => lambda operator, and lambda expressions are frequently used in LINQ expressions. As you will see in the course of this book, the combination of LINQ and lambda expressions represents a radically powerful subset of C#. Furthermore, they are revolutionary features thatxxiii 24. xxivC# 3.0: The Complete Referenceare redefining how solutions are crafted for many different types of programming tasks, not just database queries. In essence, they let you approach old problems in new ways. Their use not only streamlines a solution, but also helps you conceptualize a problem from a different point of view. Simply put, the addition of LINQ and lambda expressions is both significant and far reaching. They are changing the way we think about the job of programming. Because of its ability to adapt rapidly to the changing demands of the programming landscape, C# has remained a vibrant and innovative language. As a result, it defines one of the most powerful, feature-rich languages in modern computing. It is also a language that no programmer can afford to ignore. This book is designed to help you master it.Whats Inside This book describes C# 3.0. It is divided into two parts. Part I provides a comprehensive discussion of the C# language, including the new features added by version 3.0. This is the largest part in the book, and it describes the keywords, syntax, and features that define the language. I/O, file handling, reflection, and the preprocessor are also discussed in Part I. Part II explores the C# class library, which is the .NET Framework class library. This library is huge! Because of space limitations, it is not possible to cover the entire .NET Framework class library in one book. Instead, Part II focuses on the core library, which is contained in the System namespace. Also covered are collections, multithreading, networking, and Windows Forms. These are the parts of the library that nearly every C# programmer will use.A Book for All Programmers This book does not require any previous programming experience. If you already know C++ or Java, you will be able to advance quite rapidly because C# has much in common with those languages. If you dont have any previous programming experience, you will still be able to learn C# from this book, but you will need to work carefully through the examples in each chapter.Required Software To compile and run C# 3.0 programs, you must use Visual Studio 2008 or later.Dont Forget: Code on the Web Remember, the source code for all of the programs in this book is available free-of-charge on the Web at www.mhprofessional.com. 25. PrefaceFor Further Study C# 3.0: The Complete Reference is your gateway to the Herb Schildt series of programming books. Here are some others that you will find of interest. For a carefully paced introduction to C#, try C# 3.0: A Beginners Guide To learn about Java programming, we recommend the following: Java: The Complete Reference Java: A Beginners Guide Swing: A Beginners Guide The Art of Java Herb Schildts Java Programming Cookbook To learn about C++, you will find these books especially helpful: C++: The Complete Reference C++: A Beginners Guide C++ From the Ground Up STL Programming From the Ground Up The Art of C++ Herb Schildts C++ Programming Cookbook If you want to learn about the C language, the foundation of all modern programming, the following title will be of interest: C: The Complete ReferenceWhen you need solid answers, fast, turn to Herbert Schildt, the recognized authority on programming.xxv 26. This page intentionally left blank 27. IPARTThe C# LanguageCHAPTER 1 The Creation of C#CHAPTER 2 An Overview of C#Part I discusses the elements of the C# language, including its keywords, syntax, and operators. Also described are several foundational C# techniques, such as using I/O and reflection, which are tightly linked with the C# language.CHAPTER 3 Data Types, Literals, and VariablesCHAPTER 4 OperatorsCHAPTER 5 Program Control StatementsCHAPTER 6 Introducing Classes and ObjectsCHAPTER 7 Arrays and StringsCHAPTER 8 A Closer Look at Methods and ClassesCHAPTER 9 Operator OverloadingCHAPTER 10 Indexers and PropertiesCHAPTER 11 InheritanceCHAPTER 12 Interfaces, Structures, and EnumerationsCHAPTER 13 Exception HandlingCHAPTER 14 Using I/OCHAPTER 15 Delegates, Events, and Lambda ExpressionsCHAPTER 16 Namespaces, the Preprocessor, and AssembliesCHAPTER 17 Runtime Type ID, Reection, and AttributesCHAPTER 18 GenericsCHAPTER 19 LINQCHAPTER 20 Unsafe Code, Pointers, Nullable Types, and Miscellaneous Topics 28. This page intentionally left blank 29. 1CHAPTERThe Creation of C#C# is Microsofts premier language for .NET development. It leverages time-tested features with cutting-edge innovations and provides a highly usable, efficient way to write programs for the modern enterprise computing environment. It is, by any measure, one of the most important languages of the 21st century. The purpose of this chapter is to place C# into its historical context, including the forces that drove its creation, its design philosophy, and how it was influenced by other computer languages. This chapter also explains how C# relates to the .NET Framework. As you will see, C# and the .NET Framework work together to create a highly refined programming environment.C#s Family Tree Computer languages do not exist in a void. Rather, they relate to one another, with each new language influenced in one form or another by the ones that came before. In a process akin to cross-pollination, features from one language are adapted by another, a new innovation is integrated into an existing context, or an older construct is removed. In this way, languages evolve and the art of programming advances. C# is no exception. C# inherits a rich programming legacy. It is directly descended from two of the worlds most successful computer languages: C and C++. It is closely related to another: Java. Understanding the nature of these relationships is crucial to understanding C#. Thus, we begin our examination of C# by placing it in the historical context of these three languages.C: The Beginning of the Modern Age of Programming The creation of C marks the beginning of the modern age of programming. C was invented by Dennis Ritchie in the 1970s on a DEC PDP-11 that used the UNIX operating system. While some earlier languages, most notably Pascal, had achieved significant success, C established the paradigm that still charts the course of programming today. C grew out of the structured programming revolution of the 1960s. Prior to structured programming, large programs were difficult to write because the program logic tended to degenerate into what is known as spaghetti code, a tangled mass of jumps, calls, and returns that is difficult to follow. Structured languages addressed this problem by adding well-defined control statements, subroutines with local variables, and other improvements. Through the use of structured techniques programs became better organized, more reliable, and easier to manage.3 30. 4Part I:The C# LanguageAlthough there were other structured languages at the time, C was the first to successfully combine power, elegance, and expressiveness. Its terse, yet easy-to-use syntax coupled with its philosophy that the programmer (not the language) was in charge quickly won many converts. It can be a bit hard to understand from todays perspective, but C was a breath of fresh air that programmers had long awaited. As a result, C became the most widely used structured programming language of the 1980s. However, even the venerable C language had its limits. One of the most troublesome was its inability to handle large programs. The C language hits a barrier once a project reaches a certain size, and after that point, C programs are difficult to understand and maintain. Precisely where this limit is reached depends upon the program, the programmer, and the tools at hand, but there is always a threshold beyond which a C program becomes unmanageable.The Creation of OOP and C++ By the late 1970s, the size of many projects was near or at the limits of what structured programming methodologies and the C language could handle. To solve this problem, a new way to program began to emerge. This method is called object-oriented programming (OOP). Using OOP, a programmer could handle much larger programs. The trouble was that C, the most popular language at the time, did not support object-oriented programming. The desire for an object-oriented version of C ultimately led to the creation of C++. C++ was invented by Bjarne Stroustrup beginning in 1979 at Bell Laboratories in Murray Hill, New Jersey. He initially called the new language C with Classes. However, in 1983 the name was changed to C++. C++ contains the entire C language. Thus, C is the foundation upon which C++ is built. Most of the additions that Stroustrup made to C were designed to support object-oriented programming. In essence, C++ is the object-oriented version of C. By building upon the foundation of C, Stroustrup provided a smooth migration path to OOP. Instead of having to learn an entirely new language, a C programmer needed to learn only a few new features before reaping the benefits of the object-oriented methodology. C++ simmered in the background during much of the 1980s, undergoing extensive development. By the beginning of the 1990s, C++ was ready for mainstream use, and its popularity exploded. By the end of the decade, it had become the most widely used programming language. Today, C++ is still the preeminent language for the development of high-performance system code. It is critical to understand that the invention of C++ was not an attempt to create an entirely new programming language. Instead, it was an enhancement to an already highly successful language. This approach to language developmentbeginning with an existing language and moving it forwardestablished a trend that continues today.The Internet and Java Emerge The next major advance in programming languages is Java. Work on Java, which was originally called Oak, began in 1991 at Sun Microsystems. The main driving force behind Javas design was James Gosling. Patrick Naughton, Chris Warth, Ed Frank, and Mike Sheridan also played a role. Java is a structured, object-oriented language with a syntax and philosophy derived from C++. The innovative aspects of Java were driven not so much by advances in the art of programming (although some certainly were), but rather by changes in the computing environment. Prior to the mainstreaming of the Internet, most programs were written, 31. Chapter 1:The Creation of C#The Creation of C# While Java has successfully addressed many of the issues surrounding portability in the Internet environment, there are still features that it lacks. One is cross-language interoperability, also called mixed-language programming. This is the ability for the code produced by one language to work easily with the code produced by another. Cross-language interoperability is needed for the creation of large, distributed software systems. It is also desirable for programming software components because the most valuable component is one that can be used by the widest variety of computer languages, in the greatest number of operating environments.PART I PART I PART Icompiled, and targeted for a specific CPU and a specific operating system. While it has always been true that programmers like to reuse their code, the ability to port a program easily from one environment to another took a backseat to more pressing problems. However, with the rise of the Internet, in which many different types of CPUs and operating systems are connected, the old problem of portability reemerged with a vengeance. To solve the problem of portability, a new language was needed, and this new language was Java. Although the single most important aspect of Java (and the reason for its rapid acceptance) is its ability to create cross-platform, portable code, it is interesting to note that the original impetus for Java was not the Internet, but rather the need for a platform-independent language that could be used to create software for embedded controllers. In 1993, it became clear that the issues of cross-platform portability found when creating code for embedded controllers are also encountered when attempting to create code for the Internet. Remember: the Internet is a vast, distributed computing universe in which many different types of computers live. The same techniques that solved the portability problem on a small scale could be applied to the Internet on a large scale. Java achieved portability by translating a programs source code into an intermediate language called bytecode. This bytecode was then executed by the Java Virtual Machine (JVM). Therefore, a Java program could run in any environment for which a JVM was available. Also, since the JVM is relatively easy to implement, it was readily available for a large number of environments. Javas use of bytecode differed radically from both C and C++, which were nearly always compiled to executable machine code. Machine code is tied to a specific CPU and operating system. Thus, if you wanted to run a C/C++ program on a different system, it needed to be recompiled to machine code specifically for that environment. Therefore, to create a C/C++ program that would run in a variety of environments, several different executable versions of the program would be needed. Not only was this impractical, it was expensive. Javas use of an intermediate language was an elegant, cost-effective solution. It is also a solution that C# would adapt for its own purposes. As mentioned, Java is descended from C and C++. Its syntax is based on C, and its object model is evolved from C++. Although Java code is neither upwardly nor downwardly compatible with C or C++, its syntax is sufficiently similar that the large pool of existing C/C++ programmers could move to Java with very little effort. Furthermore, because Java built upon and improved an existing paradigm, Gosling, et al., were free to focus their attention on the new and innovative features. Just as Stroustrup did not need to reinvent the wheel when creating C++, Gosling did not need to create an entirely new language when developing Java. Moreover, with the creation of Java, C and C++ became an accepted substrata upon which to base a new computer language.5 32. 6Part I:The C# LanguageAnother feature lacking in Java is full integration with the Windows platform. Although Java programs can be executed in a Windows environment (assuming that the Java Virtual Machine has been installed), Java and Windows are not closely coupled. Since Windows is the most widely used operating system in the world, lack of direct support for Windows is a drawback to Java. To answer these and other needs, Microsoft developed C#. C# was created at Microsoft late in the 1990s and was part of Microsofts overall .NET strategy. It was first released in its alpha version in the middle of 2000. C#s chief architect was Anders Hejlsberg. Hejlsberg is one of the worlds leading language experts, with several notable accomplishments to his credit. For example, in the 1980s he was the original author of the highly successful and influential Turbo Pascal, whose streamlined implementation set the standard for all future compilers. C# is directly related to C, C++, and Java. This is not by accident. These are three of the most widely usedand most widely likedprogramming languages in the world. Furthermore, at the time of C#s creation, nearly all professional programmers knew C, C++, and/or Java. By building C# upon a solid, well-understood foundation, C# offered an easy migration path from these languages. Since it was neither necessary nor desirable for Hejlsberg to reinvent the wheel, he was free to focus on specific improvements and innovations. The family tree for C# is shown in Figure 1-1. The grandfather of C# is C. From C, C# derives its syntax, many of its keywords, and its operators. C# builds upon and improves the object model defined by C++. If you know C or C++, then you will feel at home with C#. C# and Java have a bit more complicated relationship. As explained, Java is also descended from C and C++. It too shares the C/C++ syntax and object model. Like Java, C# is designed to produce portable code. However, C# is not descended from Java. Instead, C# and Java are more like cousins, sharing a common ancestry, but differing in many important ways. The good news, though, is that if you know Java, then many C# concepts will be familiar. Conversely, if in the future you need to learn Java, then many of the things you learn about C# will carry over. C# contains many innovative features that we will examine at length throughout the course of this book, but some of its most important relate to its built-in support for software components. In fact, C# has been characterized as being a component-oriented language because it contains integral support for the writing of software components. For example, FIGURE 1-1 The C# family tree 33. Chapter 1:The Creation of C#The Evolution of C# Since its original 1.0 release, C# has been evolving at a rapid pace. Not long after C# 1.0, Microsoft released version 1.1. It contained many minor tweaks but added no major features. However, the situation was much different with the release of C# 2.0. C# 2.0 was a watershed event in the lifecycle of C# because it added many new features, such as generics, partial types, and anonymous methods, that fundamentally expanded the scope, power, and range of the language. Version 2.0 firmly put C# at the forefront of computer language development. It also demonstrated Microsofts long-term commitment to the lang