a0016 visual c sharp net programming 2002 morebook vn 8996

The Structure of This Book: About the Musical Part Names Since C# is a programming language named after a musical note, I thought it appropriate to involve musical concepts when struct

Visual C# NET Programming

Harold Davis

Associate Publisher: Richard Mills

Acquisitions Editor: Denise Santoro Lincoln

Developmental Editor: Tom Cirtin

Editor: Pete Gaughan

Production Editor: Mae Lum

Technical Editor: Matt Tagliaferri

Electronic Publishing Specialists: Rozi Harris, Bill Clark, Interactive Composition

Corporation

Proofreaders: Amey Garber, Nelson Kim, David Nash, Laurie O'Connell, Yariv Rabinovitch, Nancy Riddiough

Indexer: Lynnzee Elze

Cover Designer: Caryl Gorska, Gorska Design

Cover Photographer: Carlog Navajas, Image Bank

Copyright © 2002 Harold Davis

World rights reserved No part of this publication may be stored in a retrieval system,

transmitted, or reproduced in any way, including but not limited to photocopy, photograph, magnetic, or other record, without the prior agreement and written permission of the

publisher

Figures 2.1, 2.2, 8.4, 10.6, and 12.16 Copyright © 2002, Phyllis Davis All rights reserved Library of Congress Card Number: 2002106412

ISBN: 0-7821-4046-7

SYBEX and the SYBEX logo are either registered trademarks or trademarks of SYBEX Inc

in the United States and/or other countries

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TRADEMARKS: SYBEX has attempted throughout this book to distinguish proprietary trademarks from descriptive terms by following the capitalization style used by the

manufacturer

The author and publisher have made their best efforts to prepare this book, and the content is based upon final release software whenever possible Portions of the manuscript may be based

upon pre-release versions supplied by software manufacturer(s) The author and the publisher make no representation or warranties of any kind with regard to the completeness or accuracy

of the contents herein and accept no liability of any kind including but not limited to

performance, merchantability, fitness for any particular purpose, or any losses or damages of any kind caused or alleged to be caused directly or indirectly from this book

Manufactured in the United States of America

10 9 8 7 6 5 4 3 2 1

For Phyllis, who makes the music in my life

Acknowledgments

When the music stops, an author alone is responsible for the book he or she has created That said, a book such as this is produced through the efforts of many people Richard Mills and Denise Santoro Lincoln originated this project and brought me into it Tom Cirtin did a great job of helping to birth this book, and contributed from his vast store of musical knowledge Mae Lum masterfully handled the logistics as the book became a full-fledged project Pete Gaughan copyedited this book and has substantially helped to make it something we can all

be proud of Matt Tagliaferri provided technical review and helped save me from myself

In addition to team Sybex, I would like to thank my friend and agent, Matt Wagner, and Bill Gladstone, both of Waterside Productions

I am thankful to Phyllis Davis, who contributed beyond the call of duty in a number of ways, and to Martin Davis, who read several chapters in 'manuscript,' as they quaintly say, and made many useful suggestions And thanks to Chris Hopper, who helped with hardware

Last, but not least, a standing ovation for Anders Hejlsberg and Scott Wiltamuth, without whom there would be no C# to write about

The quotation on the bottom of the front cover is taken from the thirty-fifth chapter of Lao Tzu'sTao Te Ching, the classic work of Taoist philosophy This particular verse is from the translation byD C Lau (copyright 1963) and communicates a theme explored throughout the book: true knowledge transcends the ordinary senses

It is traditionally held that Lao Tzu lived in the fifth century B.C in China, during the Chou dynasty, but it is unclear whether he was actually a historical figure It is said that he was a teacher of Confucius The concepts embodied in the Tao Te Ching influenced religious

thinking in the Far East, including Zen Buddhism in Japan Many in the West, however, have wrongly understood theTao Te Ching to be primarily a mystical work; in fact, much of the advice in the book is grounded in a practical moral philosophy governing personal conduct

Introduction

I dreamed that black-clad horsemen pursued me down a lonely road The hoofs of their steeds rang with urgent clanks on the paving stones I turned to look at my pursuers and saw fiery red-rimmed eyes fixed within deathly pale faces A sword was raised, and as it swept down…

No, that's not the way it goes at all

I dreamed of a city far in the future Sentient machines performed all menial labor, so there was plenty of time for science and art But all was not well in paradise Regimentation begat alienation, and alienation begat a class of cyber-hackers who had dropped out of known society and lived in caves far from the city

That's a little closer, but we're not quite there yet! Let's try again

I dreamed of a pure programming language, so sweet and tender, yet flexible and strong This language, named after a musical note, incorporated the best features of other languages and also made available an extremely potent library of classes You guessed it: the language is C#, and the library of classes the NET Framework This dream is true!

This is a different kind of book about a programming language The conventional thing is to begin with syntax and semantics, proceed through user interfaces and object orientation, and end with various applications But why be conventional? This book does not do the standard thing

To some degree, a book is a compact between writer and reader The reader will rightly be disappointed if what they expected to find is missing At the same time, no book can be everything for everybody

In this sense, the compact between writer and reader is analogous to the implementation of an interface in a class Everything is spelled out in the interface, so that there is no

misunderstanding about how to use an implementation of it

I expect readers of this book to have some experience with programming, or at least be highly intelligent This is not a book for dummies (Or, as Mel Brooks exhorted in a different

context, 'Be a smarty!')

However, your programming experience need not be with a language in the 'C' family-or even with Java C# represents a wonderful 'next step' for Visual Basic programmers If you are a

VB programmer looking for new horizons, this book was written for you

By the way, the one area that seems to trip VB programmers new to C# is type conversion So

if you are a VB programmer new to C#, you might want to start with a look at the material explaining type conversion in Chapter 6, 'Zen and Now: The C# Language.'

I do not promise to be comprehensive or encyclopedic in my coverage of C# or the NET Framework For one thing, no single book could ever keep this promise, as the field is so vast For another, online help is the best place for detailed answers to many questions-so, as

appropriate in this book, I refer you to help topics

Internal tools such as the Object Browser reveal more information than any documentation could-I show you how to make the best use of the Object Browser in Chapter 5, 'Reflecting on Classes.'

Finally, most serious programmers-or students of a programming language-have multiple books about the language on their shelves: In other words, comprehensiveness is found in libraries, and in online compendiums, not individual books

So if I don't promise to be comprehensive, what commitments am I making?

First, regarding the code in the book: I've tried to provide examples that you will be able to use in the real world, based on my experience as a developer I've run and tested every

example in the book Many of the examples should be usable in whole or part as they are written

C# is a graceful language I've tried to write about it in an intelligent, elegant, and humorous way

I hope you enjoy this book C# NET is a powerful, exciting, easy-to-use programming

language The primary goals of my book are to:

• Share my excitement and joy in this aesthetically pleasing and productive tool

• Help you to understand the concepts involved in programming with C# and the NET Framework

• Help you easily produce the code that you need for real projects

If you read through this book and follow the examples, you will learn a lot In contrast to the conventional structure of the programming language book, described earlier in this

introduction, the narrative structure of this book involves immersion You'll learn by doing-starting with creating a web service in the first few pages It's only later that the nitty-gritty of language syntax is covered in detail The idea is that you'll be having so much fun by then that the pain of mastering the details will be muted

While we're on the subject of narrative structure-and, yes, Virginia, even computer books do have narrative structure-let's talk about the musical part names of this book

The Structure of This Book: About the Musical Part

Names

Since C# is a programming language named after a musical note, I thought it appropriate to involve musical concepts when structuring this book In keeping with this, I've named each

of the four parts of the book after movements in a classical composition These movements- prelude, allemande, courante, and gigue-primarily are found in Baroque music Musical scholars should note that I have not been compulsive about the accuracy or consistency of the musical metaphor The point really is the metaphor and how it relates to the structure of this book and to programming in C#

The structure of the book is essentially spiral, like a chambered nautilus shell or the pattern in this volume's cover photograph of a Zen garden By the end of the book, readers will be able

to comprehend and accomplish things that seemed shadowy and mysterious when they

plunged in at the beginning Each of the four parts represents a different stage in this quest for skills and understanding

Part 1 : Prelude-Service with a Smile

In classical music, the prelude introduces the work Often composed in a free-flowing style, it sets the mood and mode for the rest of the work and is designed to pique the interest of the audience It can contain references to ideas that are delivered later-foreshadowings, a taste

of things to come The themes in the prelude are not whole ideas but snippets, motifs-just

enough to whet the appetite and make the listener want more These motifs are pre-echoes- not déjà vu, which are vague memories of things already seen, but rather premonitions of things to come If you listen to the composition more than once, then in the prelude you should be able to begin to hear the pattern of the entire piece

At the same time that a prelude introduces the larger work; it is an organic unit in and of itself, with a beginning, middle, and end This cohesive mini-composition exists within the larger whole and has its own sense of narrative conflict and resolution, point and

counterpoint, all reconciling in a conclusion that serves as an introduction

Our prelude introduces the theme of the web service Web services have been hailed by some

as revolutionary: a brand new kind of unit of executable code, fit for the distributed

environments of the Internet age

A web service is not an end in and of itself To actually do anything as a part of a program, it must be used-or, put another way, 'consumed.'

It is also the case that this book is not 'about' web services; it is about programming in the C# language and the NET Framework

Our prelude explores creating a web service, in Chapter 1, 'Creating a Web Service,' and coding ASP.NET web applications to consume the web service, in Chapter 2, 'Consuming the Service on the Web,' as a dramatic way to jump into the topics that will form the pattern of the composition that is this book Keep your eyes and ears open for premonitions that reveal this book's real themes: the best way to write C# code for clarity, and patterns and practice of communication between objects

Part II : Allemande-Striding Forward

The allemande is a movement of great substance that directly follows the prelude of a musical suite and picks up where the prelude leaves off It is stately in manner and can be highly stylized The allemande carries forward the mood prefigured in the prelude and introduces gravity into the suite; but the prelude's free style gives way to the processional-like regularity

of the allemande

The sentiments casually introduced in the prelude have become a stepping dance with reality-and the allemreality-ande keeps it all moving The meter is steady reality-and so is the progress

The allemande is striding forward without hesitation into the future, and the future is now Early allemandes come in three sections, or strains, that are related but not the same The second strain contrasts with the first strain They resolve in the third and final section, which paves the way for the next movement in the composition

You'll also find the Previous Topic and Next Topic features helpful These appear in the toolbar as an up arrow (Previous topic) and a down arrow (Next topic) These let you scan the help in the order of the help contents

Filtering Help Results

As I noted in the section on the Contents window, help results can be filtered using the

Filtered By drop-down list in the Contents, Index, or Search window

To turn filtering off, select '(no filter)' in this drop-down list However, it is likely that you will wish to filter by Visual C# or Visual C# And Related, simply to keep your help searches manageable

Tip NET Framework SDK is another very useful filter

Note You can also set the help filter on your Start page To do this, show your Start page by selecting Help → Show Start Page With the Start page open, select My Profile, and set the Help Filter using the drop-down box

It is an interesting fact that you can customize filters and create new filters using Boolean criteria, as though you were writing the WHERE clause of a SQL query (which is likely exactly what you are doing under the covers!)

To open the Edit Help Filters window, select Help → Edit Filters Using this window, you can edit the definition of a current filter or select New from the menu bar to create a new filter To edit a filter, first select it in the Filter drop-down list Figure A.5 shows an example of the Edit Help Filters window with the Visual C# And Related filter selected

Figure A.5: You can use the Edit Help Filters window to customize help filters using a

Boolean syntax

At the bottom of the Edit Help Filters window, you'll find a list of the available attributes that can be used together with Boolean operators to create a filter definition Figure A.6 shows an excerpt from this list

Figure A.6: Use the attribute list to edit your filter definitions

To find out how many topics are included in a given filter, click the Calculate button in the Edit Help Filters window For example, you may find it relevant to know that the Visual C# filter has 8,093 topics, and the Visual C# And Related filter has 53,311 topics This gives you

an idea of the comparative breadth of each topic (both totals are slightly less than those yielded by the comparable VB NET filter)