Beginning C# Objects: From Concepts to Code JACQUIE BARKER AND GRANT PALMER APress Media, LLC Beginning C# Objects: From Concepts to Code Copyright ©2004 by Jacquie Barker and Grant Palmer Originally published by Apress in 2004 AII 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 978-1-59059-360-8 ISBN 978-1-4302-0691-0 (eBook) DOI 10.1007/978-1-4302-0691-0 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: Dominic Shakeshaft Technical Reviewer: James Huddleston Editorial Board: Steve Anglin, Dan Appleman, Ewan Buckingham, Gary Cornell, Tony Davis, John Franklin, Jason Gilmore, Chris Mills, Steve Rycroft, Dominic Shakeshaft, Jim Sumser, Karen Watterson, Gavin Wray, John Zukowski Project Manager: Kylie Johnston Copy Edit Manager: Nicole LeClerc Copy Editor: Ami Knox Production Manager: Kari Brooks Production Editor: Laura Cheu Compositor: Kinetic Publishing Services, LLC Proofreader: Liz Welch Indexer: Michael Brinkman Artist: Kinetic Publishing Services, LLC Cover Designer: Kurt Krames Manufacturing Manager: Tom Debolski The information in this book is distributed on an "as is" hasis, without warranty. 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In loving memory of my wonderful parents, Bill and Dorothy lost. -Jacquie Barker I would like to dedicate this book to my dog Bailey, who is a good, old dog. -Grant Palmer Contents at a Glance About the Authors ................................................ xiii Acknowledgments .................................................... xv Preface ........................................................... xvii Introduction ...................................................... xix Part One: The ABCs of Objects ............................ . 1 Chapter 1 A little Taste of C# ................................ 3 Chapter 2 Abstraction and Modeling .......................... 55 Chapter 3 Objects and Classes ................................ 69 Chapter 4 Object Interactions ................................ 91 Chapter 5 Relationships Between Objects .................... 159 Chapter 6 Collections of Objects ............................ 201 Chapter 7 Some Final Object Concepts ....................... 237 Part Two: Object Modeling 101 ........................... 293 Chapter 8 The Object Modeling Process in a Nutshell ...... 295 Chapter 9 Formalizing Requirements Through Use Cases ..... 307 Chapter 10 Modeling the Static/Data Aspects of the System .............................................. 321 Chapter 11 Modeling the Dynamic/Behavioral Aspects of the System ......................................... 383 Chapter 12 Wrapping Up Our Modeling Efforts ................ 409 Part Three:Translating a UML "Blueprint" into C# Code ............................................... 419 Chapter 13 A Deeper Look at C# ............................... 421 Chapter 14 Transforming Our UML Model into C# Code ........ 547 Chapter 15 Rounding Out Our Application, Part 1: Adding File Persistence .......................... 611 v Contents at a Glance Chapter 16 Rounding Out Our Application, Part 2: Adding a Graphical User Interface ............... 667 Chapter 17 Next Steps ......................................... 763 Appendix A Suggestions for Using This Book As a Textbook ......................................... 769 Appendix B Alternative Case Studies ......................... 775 Appendix C Setting Up a Basic Object Modeling/C# Environment ........................................ 783 Appendix D Downloading and Compiling the SRS Source Code ........................................ 791 Appendix E C# Keywords ........................................ 793 Index ............................................................. . 799 vi Contents About the Authors ................................................ xiii Acknowledgments .................................................... xv Preface ........................................................... xvii Introduction ...................................................... xix Part One: The ABCs of Objects Chapter 1 A Little Taste of C# .......................... 3 Getting "Hands On" with C# ........................................ 4 Why C#? ............................................................. 4 C# Language Basics ................................................. 7 Anatomy of a Simple C# Program ................................... B Predefined Types .................................................. 11 Variables .......................................................... 12 Strings ............................................................ . 15 Case Sensitivity .................................................. 16 C# Expressions ..................................................... 16 Implicit Type Conversions and Explicit Casting ................ 22 Loops and Other Flow of Control Structures .................... 24 Jump Statements .......................... 36 0. 0 0 ••• 0 0 0 0 0 0 •• 0 ••••••••• Code Blocks and Variable Scope .................................. 37 Printing to the Screen .... 39 0 ••••••••••••••••• 0 •••••••••••••••••••• Elements of C# Style .............................................. 43 Summary 51 0 •••• 0 •••••• 0 •• 0 ••••••••••••••••••••••••••••••••••••••••••••• Exercises .......................................................... 52 Chapter 2 Abstraction and Modeling .................... 55 Simplification Through Abstraction .............................. 55 Generalization Through Abstraction .............................. 56 Reuse of Abstractions ........................... 62 0 ••••••••••••••••• Inherent Challenges ....................................... 63 0 ••••••• Summary ............................... 66 0 ••••••••••••••••••••••••••••• Exercises .......................................................... 66 Chapter 3 Objects and Classes ........................... 69 What Is an Object? ................................................ 69 State/A ttributes/Data ............................................. 70 vii Contents Behavior /Operations/Methods ...................................... 72 Classes ............................................................. 74 User-Defined Types and Reference Variables ..................... 79 Instantiating Objects: A Closer Look ........................... 80 Objects As Attributes ............................................. 84 Composition ........................................................ 86 Three Distinguishing Features of an Object-Oriented Programming Language ........................................... 89 Summary ............................................................. 89 Exercises .......................................................... 90 Chapter 4 Object Interactions ........................... 91 Events Drive Object Collaboration ............................... 91 Declaring Methods ................................................. 93 Method Invocation and Dot Notation ............................. 102 Information Hiding/Accessibility ............................... 118 The Power of Encapsulation ...................................... 142 Instance Constructors ............................................ 151 Summary ............................................................ 155 Exercises ......................................................... 156 Chapter 5 Relationships Between Objects ............ 159 Associations and Links .......................................... 160 Inheritance ....................................................... 168 Three Distinguishing Features of an Object-Oriented Programming Language, Revisited .............................. 196 Summary ............................................................ 197 Exercises ......................................................... 197 Chapter 6 Collections of Objects ...................... 201 What Are Collections? ........................................... 201 Arrays As Simple Collections ................................... 205 More Sophisticated Collection Types ............................ 215 Referencing the Same Object Simultaneously from Multiple Collections .......................................... 220 Inventing Our Own Collection Types ............................. 221 Collections As Method Return Types ............................. 227 Collections of Supertypes ....................................... 228 Composite Classes, Revisited .................................... 230 Summary ............................................................ 234 Exercises ......................................................... 235 viii Contents Chapter 7 Some Final Object Concepts ................ 237 What Is Polymorphism? ........................................... 238 Three Distinguishing Features of an Object-Oriented Programming Language .......................................... 247 Abstract Classes ................................................. 248 Interfaces ........................................................ 256 Static Features .................................................. 271 Utility Classes .................................................. 283 Summary ............................................................ 288 Exercises ......................................................... 289 Part Two: Object Modeling 101 Chapter 8 The Object Modeling Process in a Nutshell ...................................... 295 The "Big Picture" Goal of Object Modeling .................... 295 Our Object Modeling Process, in a Nutshell ................... 300 Summary ............................................................ 304 Exercises ......................................................... 305 Chapter 9 Formalizing Requirements Through Use Cases ....................................... 307 What Are Use Cases? .............................................. 308 Actors ............................................................. 310 Spedf ying Use Cases ............................................. 315 Matching Up Use Cases with Actors .............................. 316 To Diagram or Not to Diagram? .................................. 317 Summary ............................................................ 319 Exercises ......................................................... 319 Chapter 10 Modeling the Static/Data Aspects of the System .................................. 321 Identifying Appropriate Classes ................................ 322 Producing a Data Dictionary ..................................... 336 Determining Associations Between Classes ...................... 338 Identifying Attributes .......................................... 343 UML Notation: Modeling the Static Aspects of an Abstraction .............................................. 343 Object Diagrams .................................................. 357 ix Contents Information "Flows" Along the Association "Pipeline" ........ 361 "Mixing and Matching" Relationship Notations ................. 366 Association Classes .............................................. 369 Our Completed Student Registration System Class Diagram .................................................. 372 Metadata .......................................................... 379 Summary ............................................................ 381 Exercises ......................................................... 382 Chapter 11 Modeling the Dynamic/Behavioral Aspects of the System ....................... 383 How Behavior Affects State ...................................... 384 Scenarios ......................................................... 391 Sequence Diagrams ................................................ 395 Using Sequence Diagrams to Determine Methods ................. 401 Collaboration Diagrams .......................................... 404 Revised SRS Class Diagram ....................................... 405 Summary ............................................................ 407 Exercises ......................................................... 407 Chapter 12 Wrapping Up Our Modeling Efforts ........ 409 Testing Your Model ............................................... 409 Revisiting Requirements ......................................... 410 Reusing Models: A Word About Design Patterns ................. 413 Summary ............................................................ 416 Exercises ......................................................... 417 Part Three:Translating a UML "Blueprint" into C# Code Chapter 13 A Deeper Look at C# ......................... 421 Sorting Out Terminology ......................................... 422 Setting Up a C# Programming Environment ....................... 424 Compiling and Running C# Programs .............................. 424 Namespaces ........................................................ 438 Strings As Objects ............................................... 445 C# Exception Handling ........................................... 452 The Object Class ................................................. 466 C#' s Collection Classes ......................................... 474 Initialization of Variables, Revisited ........................ 498 More About the Main Method ...................................... 500 X