Now that we have concluded our mid-chapter reprieve, let's move on to more interesting topics and

Apress © 2003 (1200 pages)

examine the details of defining custom methods for a C# class. First understand that, like points of data,

This comprehensive text starts with a brief overview of the

every method youC#implementlanguage mustand thenbe aquicklymembermovesof atoclasskey technicalor struct and(global methods are not allowed in

C#). architectural issues for .NET developers.

As you know, a method exists to allow the type to perform a unit of work. Like Main(), your custom

Tablemethodsof Contentsmay or may not take parameters, may or may not return values (of any intrinsic or user defined C#types)and.theAlso.NETcustomPlatform,methodsSecondmayEditionbe declared nonstatic (instance-level) or static (class-level) entities.

Introduction

PartMethodOne - IntroduAccessing C# andModifiersthe .NET Platform

Chapter 1 - The Philosophy of .NET

ChaptA methodr 2 -mustBuildingspecifyC# itsApplicatilevel ofnsaccessibility (see Table 3-8). C# offers the following method access

PartmodifiersTwo - The(youC#examineProgrammingthe useLanguageof protected and internal methods in the next chapter during the

Chapterdiscussion3 -ofC#classLanguagehierarchies):Fundamentals

Chapter 4 - Object-Oriented Programming with C#

Table 3-8: C# Accessibility Keywords

Chapter 5 - Exceptions and Object Lifetime

Chapter 7 - Callback Interfaces, Delegates, and Events

Modifier

Chapter 8 - Advanced C# Type Construction Techniques

PartpublicThree - ProgrammingMarkswith a.NETmethodAssembliesas accessible from an object instance, or any subclass.

Chapter 9 - Understanding .NET Assemblies

private Marks a method as accessible only by the class that has defined the

Chapter 10 - Processes, AppDomains, Contexts, and Threads

method. If you don't say otherwise, private is assumed (it is the default

Chapter 11 - Type Reflection, Late Binding, and Attribute-Based Programming visibility level).

Part Four - Leveraging the .NET Libraries

Chapter 18 - ASP.NET Web Pages and Web Controls

Here are the implications of each accessibility keyword:

Chapter 19 - ASP.NET Web Applications

Chapter 20 - XML Web Services

// Visibility options.

Index

class SomeClass

List of Figures

{

List of Tables

// Accessible anywhere.

public void MethodA(){}

// Accessible only from SomeClass types.

private void MethodB(){}

// Accessible from SomeClass and any descendent.

protected void MethodC(){}

// Accessible from within the same assembly.

internal void MethodD(){}

// Assembly-protected access.

protected internal void MethodE(){}

// Unmarked members are private by default in C#.

void MethodF(){}

}

As you may already know, methods that are declared public are directly accessible from an object

called internally by the object to help the instance get its work done (that is, private helper functions). To

Apress © 2003 (1200 pages)

illustrate, the Teenager class shown next defines two public methods, Complain() and BeAgreeable(),

This comprehensivethe text starts with a brief overview of the

each of which returns a string to object user. Internally, both methods make use of a private helper

C# language and then quickly moves to key technical and

method named GetRandomNumber(), which manipulates a private member variable of type architectural issues for .NET developers.

System.Random:

Table// Twoof Contentspublic methods, each using an internal helper function.

using System;

C# and the .NET Platform, Second Edition

class Teenager

Introduction

{

Part One - Introducing C# and the .NET Platform

// The System.Random type generates random numbers.

Chapter 1 - The Philosophy of .NET

private Random r = new Random();

Chapter 2 - Building C# Applications

public string Complain()

Part Two - The C# Programming Language

{

Chapter 3 - C# Language Fundamentals

string[] messages = new string[5]{ "Do I have to?",

Chapter 4 - Object-Oriented Programming with C#

"He started it!", "I'm too tired...",

Chapter 5 - Exceptions and Object Lifetime

"I hate school!", "You are sooo wrong." } ;

Chapter 6 - Interfaces and Collections

Chapter 7 - Callback Interfaces, Delegates, and Events

}

Chapter 8 - Advanced C# Type Construction Techniques

public string BeAgreeable()

Part Three - Programming with .NET Assemblies

{

Chapter 9 - Understanding .NET Assemblies

string[] messages = new string[3]{ "Sure! No problem!",

Chapter 10 - Processes, AppDomains, Contexts, and Threads

"Uh uh.", "I guess so." } ;

Chapter 11 - TypereturnReflection,messages[GetRandomNumber(3)];Late Binding, Attribute-Based Programming

Part Four}- Leveraging the .NET Libraries

Chapter private12 - Obj ctintSerializaGetRandomNumber(shortion the .NET Remoting LayerupperLimit)

Chapter {13 - Building a Better Window (Introducing Windows Forms)

Chapter 14 - A //BetterRandomPainting.Next()Frameworeturnsk (GDI+) a random integer

// between 0 and upperLimit.

Chapter 15 - Programming with Windows Forms Controls

return r.Next(upperLimit);

Chapter 16 - The System.IO Namespace

}

Chapter 17 - Data Access with ADO.NET

public static void Main(string[] args)

Part Five - Web Applications and XML Web Services

Console.WriteLine("\nHappy Mike says:");

Console.WriteLine("-> {0}", mike.BeAgreeable());

}

}

Obviously the benefit of defining GetRandomNumber() as a private helper method is that various parts of the Teenager class can make use of its functionality. The only alternative would be to duplicate the random number logic within the Complain() and BeAgreeable() methods (which in this case would not be too traumatic, but assume GetRandomNumber() contains 20 or 30 lines of code). Figure 3-14 shows a possible test run.

Second Edition

ISBN:1590590554

with a brief overview of the moves to key technical and

developers.

Table

C# and

Part

Chapter

Chapter

Part

ChapterFigure3 - 3C#-14:LanguageRandomFundamentalsteenager chatter

Chapter 4 - Object-Oriented Programming with C#

Note The System.Random type is used to generate and manipulate random numbers.

Chapter 5 - Exceptions and Object Lifetime

Random.Next() method returns a number between 0 and the specified upper limit. As you would

Chapter 6 - Interfaces and Collections

guess, the Random type provides additional members, all of which are documented within

Chapter 7 - Callback Interfaces, Delegates, and Events

MSDN.

Chapter 8 - Advanced C# Type Construction Techniques

Part Three - Programming with .NET Assemblies

SOURCE The Teenager application is located under the Chapter 3 subdirectory.

Chapter 9 - Understanding .NET Assemblies

CODE

Chapter 10 - Processes, AppDomains, Contexts, and Threads

Chapter 11 - Type Reflection, Late Binding, and Attribute-Based Programming

Part Four - Leveraging the .NET Libraries

Chapter 12 - Object Serialization and the .NET Remoting Layer

Chapter 13 - Building a Better Window (Introducing Windows Forms)

Chapter 14 - A Better Painting Framework (GDI+)

Chapter 15 - Programming with Windows Forms Controls

Chapter 16 - The System.IO Namespace

Chapter 17 - Data Access with ADO.NET

Part Five - Web Applications and XML Web Services

Chapter 18 - ASP.NET Web Pages and Web Controls

Chapter 19 - ASP.NET Web Applications

Chapter 20 - XML Web Services

Index

List of Figures

List of Tables

UnderstandingC# andStaticthe .NETMethodsPla form, Second Edition

As you have seen, methods can be declared "static." But, what exactly does it mean to be a static method?

Apress © 2003 (1200 pages)

When a method is marked with the "static" keyword, it may be called directly from the class level, and does

This comprehensive text starts with a brief overview of the

not require an objectC# languagevariable.andForthenthis veryquicklyreason,m vesMain()to keyistechnicaldeclaredandstatic to allow the runtime to invoke this function without needingarchitecturalto allocateissues fora new.NETinstancedevelopersof the. defining class. This is a good thing of course, or else you would need to create an object to create an object to create an object to (...).

TableYouofshouldContentsalso consider our good friend System.Console. As you have seen, you do not invoke the

C#WriteLine()and the .NETmethodPlatfofromm, Secondan objectEditioninstance:

Introduction

Part// OneNo!- IntroducingWriteLine()C# andnottheinstance.NET Platformlevel...

ChapterConsole1 -cThe= Philosophynew Console();of .NET

Chapterc.WriteLine("I2 - Building C#can'tApplicationsbe printed...");

Part Two - The C# Programming Language

Chapter 3 - C# Language Fundamentals

but instead simply prefix the type name to the static WriteLine() member.

Chapter 4 - Object-Oriented Programming with C# Chapter 5 - Exceptions and Object Lifetime

// Yes! WriteLine() is static...

Chapter 6 - Interfaces and Collections

Console.WriteLine("Thanks...");

Chapter 7 - Callback Interfaces, Delegates, and Events

Chapter 8 - Advanced C# Type Construction Techniques

Part Three - Programming with .NET Assemblies

Simply put, static members are methods that are deemed (by the class designer) to be so commonplace that

Chapter 9 - Understanding .NET Assemblies

there is no need to create an instance of the type. When you are designing your custom class types, you are

Chapter 10 - Processes, AppDomains, Contexts, and Threads

also able to define any number of static and/or instance level members. To illustrate custom static methods,

Chapter 11 - Type Reflection, Late Binding, and Attribute-Based Programming

assume I have reconfigured the Complain() and BeAgreeable() methods of the Teenager class as follows:

Part Four - Leveraging the .NET Libraries

Chapter 12 - Object Serialization and the .NET Remoting Layer

// Teenagers complain so often, there is no need to create an initial object...

Chapter 13 - Building a Better Window (Introducing Windows Forms) publicstatic string Complain()

Chapter 14 - A Better Painting Framework (GDI+)

{

Chapter 15 - Programming with Windows Forms Controls

string[] messages = new string[5]{ "Do I have to?",

Chapter 16 - The System.IO Namespace

"He started it!", "I'm too tired...",

Chapter 17 - Data Access with ADO.NET

"I hate school!", "You are sooo wrong." } ;

Part Five - Web Applications and XML Web Services

return messages[GetRandomNumber(5)];

Chapter 18 - ASP.NET Web Pages and Web Controls

}

Chapterpublic19static- ASP.NETstringWeb ApplicationsBeAgreeable()

Chapter{ 20 - XML Web Services

Index string[] messages = new string[3]{ "Sure! No problem!",

"Uh uh.", "I guess so." };

List of Figures

return messages[GetRandomNumber(3)];

List of Tables

}

This update also assumes that the System.Random and GetRandomNumber() helper function method have also been declared as static members of the Teenager class, given the rule that static members can only operate on other static members:

class Teenager

{

private static Random r = new Random();

private static int GetRandomNumber(short upperLimit)

{ return r.Next(upperLimit); }

...

}

These assumptions aside, the process of calling a static method is simple. Just append the member to the

C# and the .NET Platform, Second Edition name of the defining class:

Apress © 2003 (1200 pages)

// Call the static Complain method of the Teenager class.

public static void Main(string[] args)

C# language and then quickly moves to key technical and

{architectural issues for .NET developers.

for(int i = 0; i < 40; i++)

Console.WriteLine("-> {0}", Teenager.Complain());

Table} of Contents

C# and the .NET Platform, Second Edition

Introduction

Part One - Introducing C# and the .NET Platform

Again, by contrast, nonstatic (instance) methods are scoped at the object level. Thus, if Complain() was not

Chapter 1 - The Philosophy of .NET

marked static, you would need to create an instance of the Teenager class before you could hear about the

Chapter 2 - Building C# Applications gripe of the day:

Part Two - The C# Programming Language

Chapter 3 - C# Language Fundamentals

// Must make an instance of Teenager class to call instance methods.

Chapter 4 - Object-Oriented Programming with C#

Chapter 5 - Exceptions and Object Lifetime

joe.Complain();

Chapter 6 - Interfaces and Collections

Chapter 7 - Callback Interfaces, Delegates, and Events

Chapter 8 - Advanced C# Type Construction Techniques

Part ThreeSOURCE- ProgrammingThewithStaticTeenager.NET Assembliesapplication is located under the Chapter 3 subdirectory.

ChapterCODE9 - Understanding .NET Assemblies

Chapter 10 - Processes, AppDomains, Contexts, and Threads

Chapter 11 - Type Reflection, Late Binding, and Attribute-Based Programming

Defining Static Data

Part Four - Leveraging the .NET Libraries

Chapter 12 - Object Serialization and the .NET Remoting Layer

In addition to static methods, a C# class may also define static data (such as the previous Random member Chvariablepter 13from- Buildingthe TeenagerBett rexample)Window (Introducing. Typically, aWindowsclass definesForm )a set of nonstatic state data. This simply

Chaptermeans14that- eachA BetterobjectPaintinginstanceFrameworkmaintains(GDI+)a private copy of the underlying values. Thus, if you have a class

Chapterdefined15as-follows:Pr gramming with Windows Forms Controls

Chapter 16 - The System.IO Namespace

Chapter 17 - Data Access with ADO.NET

// We all love Foo.

PartclassFive -FooWeb Applications and XML Web Services

Chapter{ 18 - ASP.NET Web Pages and Web Controls

Chapter public19 - ASP.NETintWebintFoo;Applications

Chapter} 20 - XML Web Services

Index

List of Figures

you can create any number of objects of type Foo and assign the intFoo field to a value to each instance:

List of Tables

// Each Foo reference maintains a copy of the intFoo field. Foo f1 = new Foo();

f1.intFoo = 100; Foo f2 = new Foo(); f2.intFoo = 993; Foo f3 = new Foo(); f3.intFoo = 6;

Static data, on the other hand, is shared among all object instances of the same type. Rather than each object holding a copy of a given field, a point of static data is allocated exactly once for all instances of the type. Assume you have a class named Airplane that contains a single point of static data. In the constructor of the Airplane class you increment this data point. Here is the initial definition:

Edition

ISBN:1590590554

brief overview of the

to key technical and

.

Table Figureof Contents3-15: Static data is shared among like objects.

C# and the .NET Platform, Second Edition

Introduction

As you can see, all instances of the Airplane class are sharing (i.e., viewing) the same integer. If one object changes the value (using either static or instance level members) all types 'see' the change. That's the point

of static data: To allow all objects to share a given value at the class (rather than at the object) level.

Chapter 2 - Building C# Applications

Part TwoSOURCE- The C# ProgrammingThe StaticDataLanguageproject is located under the Chapter 3 subdirectory.

ChapterCODE3 - C# Language Fundamentals

Chapter 4 - Object-Oriented Programming with C#

Chapter 5 - Exceptions and Object Lifetime

Chapter 6 - Interfaces and Collections

Chapter 7 - Callback Interfaces, Delegates, and Events

Chapter 8 - Advanced C# Type Construction Techniques

Part Three - Programming with .NET Assemblies

Chapter 9 - Understanding .NET Assemblies

Chapter 10 - Processes, AppDomains, Contexts, and Threads

Chapter 11 - Type Reflection, Late Binding, and Attribute-Based Programming

Part Four - Leveraging the .NET Libraries

Chapter 12 - Object Serialization and the .NET Remoting Layer

Chapter 13 - Building a Better Window (Introducing Windows Forms)

Chapter 14 - A Better Painting Framework (GDI+)

Chapter 15 - Programming with Windows Forms Controls

Chapter 16 - The System.IO Namespace

Chapter 17 - Data Access with ADO.NET

Part Five - Web Applications and XML Web Services

Chapter 18 - ASP.NET Web Pages and Web Controls

Chapter 19 - ASP.NET Web Applications

Chapter 20 - XML Web Services

Index

List of Figures

List of Tables

Method ParameterC# and the .ModifiersNET Platfo m, Second Edition

Methods tend to take parameters. If you have a COM background, you are certainly familiar with the use of

Apress © 2003 (1200 pages)

the [in], [out], and [in, out] IDL attributes. Classic COM objects use these attributes to clearly identify the

This comprehensive text starts with a brief overview of the

direction of travelC#(andlanguagememoryandallocationthen quicklyrules)movesfor atogivenk y technicalinterfaceandmethod parameter. While IDL is not used in the .NETarchitecturaluniverse, thereissuesis analogousfor .NET devbehaviorlopers.with the set of C# parameter modifiers shown in Table 3-9.

The default manner in which a parameter is sent into a function is by value. Simply put, if you do not mark an argument with a parameter-centric keyword, a copy of the data is passed into the function (the story

changes slightly when passing reference types by value, as you will see in just a bit). You have already

Chapter 16 - The System.IO Namespace

been making use of by-value parameter passing, however, here is a simple example (with implications):

Chapter 17 - Data Access with ADO.NET

Part Five - Web Applications and XML Web Services

// Default param passing is by value.

Chapter 18 - ASP.NET Web Pages and Web Controls public static int Add(int x, int y)

Chapter 19 - ASP.NET Web Applications

{

Chapter 20 - XML Web Services int ans = x + y;

Index // Caller will not see these changes.

List of Figures

x = 99999;

List of Tables

y = 88888;

return ans;

}

Here, the two value type parameters have been sent by value into the Add() method. Therefore, if we change the values of the parameters within the scope of the member, the caller is blissfully unaware, given that we are changing the values of copies of the caller's System.Int32 data types:

// Call Add() using input params.

Console.WriteLine("***** Adding 2 ints *****");

int x = 9, y = 10;

Console.WriteLine("X: {0}, Y: {1}", x, y);

Console.WriteLine("Answer is: {0}", Add(x, y));

Console.WriteLine("X: {0}, Y: {1}", x, y);

Now consider the use of the C# ref parameter modifier. Reference parameters are necessary when you

C# and the .NET Platform, Second Edition

wish to allow a method to operate on (and usually change the values of) various data points declared in

by Andrew Troelsen ISBN:1590590554

the caller's scope (such as a sort routine). Note the distinction between output and reference parameters:

Apress © 2003 (1200 pages)

Output parametersThis comprehedo not needsive textto bestarinitializeds with abeforebrief overviewthey areofsenttheto the callee. Reason? It is assumed theC#methodlanguagefillsandthe thenvaluequicklyon yourmovesbehalfto. key technical and

architectural issues for .NET developers.

Reference parameters must be initialized before being sent to the callee. Reason? You are passing a reference to an existing type. If you don't assign it to an initial value, that would be the equivalent to

Table operatingf Contents

on a NULL pointer!

C# and the .NET Platform, Second Edition

Let's check out the use of the "ref" keyword:

Introduction

Part One - Introducing C# and the .NET Platform

Chapter// Reference1 - The Philosophyparameterof .NET.

Chapterpublic2 static- BuildingvoidC# ApplicationsUpperCaseThisString(ref string s)

Part{ Two - The C# Programming Language

// Return the uppercase version of the string.

Chapter 3 - C# Language F ndamentals

// Use 'ref'.

Part Three - Programming with .NET Assemblies

string s = "Can you really have sonic hearing for $19.00?";

Chapter 9 - Understanding .NET Assemblies

Console.WriteLine("Before: {0} ", s);

Chapter 10 - Processes, AppDomains, Contexts, and Threads

UpperCaseThisString(ref s);

Chapter 11 - Type Reflection, Late Binding, and Attribute-Based Programming

Console.WriteLine("After: {0} ", s);

Part Four - Leveraging the .NET Libraries

}

Chapter 12 - Object Serialization and the .NET Remoting Layer

Chapter 13 - Building a Better Window (Introducing Windows Forms)

ChapterHere, the14 caller- A Betterhas PaintiassignedFranmeworkinitial value(GDI+)to a local string named "s." Once the call to ChaptUpperCaseThisString()15 - Programmingreturns,with Windowsthe callerFormswill findControls"s" has been converted into uppercase, given the use of

the "ref" keyword.

Chapter 16 - The System.IO Namespace

Chapter 17 - Data Access with ADO.NET

PartTheFiveC#- Web"params"Applications andKeywordXML Web Services

Chapter 18 - ASP.NET Web Pages and Web Controls

ChapterThe final19parameter- ASP.NET modifierWeb Applicationsis the "params" keyword, which is somewhat odd (but convenient) given that

it allows you to send a varied number of arguments as a singleparameter. Yes, this can be confusing. To

Chapter 20 - XML Web Services

clear the air, assume I have written a simple method defined as follows:

Index

List of Figures

List//ofThisTablesmethod has two physical parameters.

public static void DisplayArrayOfInts(string msg, params int[] list)

{

Console.WriteLine(msg);

for ( int i = 0 ; i < list.Length ; i++) Console.WriteLine(list[i]);

}

This method has been defined to take two physical parameters: one of type string, and one as a parameterized array of integers. What this method is in fact saying is, "Send me a string as the first parameter and any number of integers as the second." Given this, you can call ArrayOfInts() in any of the following ways:

// Use 'params' keyword.

int[] intArray = new int[3] {10,11,12} ;

ISBN:1590590554

of the and

Table

Figure 3-16: Passing reference types by value locks the reference in place.

C# and the .NET Platform, Second Edition

Introduction

Part One - Introducing C# and the .NET Platform

This behavior seems to fly in the face of what it means to pass a parameter "by value." Given that we were

Chapter 1 - The Philosophy of .NET

able to change the state of the incoming Person, what was copied? The answer: a copy of the reference to

Chapter 2 - Building C# Applications

the caller's object! Therefore, as the SendAPersonByValue() method is pointing to the same object as the Partcaller,Twoit-isThepossibleC# Programmingto alter the Languageobject's state data. What is not permissible is to reassign what the Chapterreference3 -isC#pointingLa uageto (slightlyFundamentalsakin to a constant pointer in C++).

Chapter 4 - Object-Oriented Programming with C#

In contrast, we have the SendAPersonByReference() method, which passes a reference type by

Chapter 5 - Exceptions and Object Lifetime

reference. As you may expect, this allows complete flexibility of how the callee is able to manipulate the

Chapter 6 - Interfaces and Collections

incoming parameter. Not only can the callee change the state of the object, but if it so chooses, it may

Chapter 7 - Callback Interfaces, Delegates, and Events

reassign the pointer! Consider the following calling logic:

Chapter 8 - Advanced C# Type Construction Techniques

Part Three - Programming with .NET Assemblies

// Passing ref-types by ref.

Chapter 9 - Understanding .NET Assemblies

Console.WriteLine("\n***** Passing person by reference *****");

Chapter 10 - Processes, AppDomains, Contexts, and Threads

Person mel = new Person("Mel", 23);

Chapter 11 - Type Reflection, Late Binding, and Attribute-Based Programming

Console.WriteLine("Before by value call, Person is:");

Part Four - Leveraging the .NET Libraries

mel.PrintInfo();

Chapter 12 - Object Serialization and the .NET Remoting Layer

Console.WriteLine("After by ref call, Person is:");

Chapter 13 - Building a Better Window (Introducing Windows Forms)

SendAPersonByReference(ref mel);

Chapter 14 - A Better Painting Framework (GDI+)

Console.WriteLine("After by value call, Person is:");

Chapter 15 - Programming with Windows Forms Controls mel.PrintInfo();

Chapter 16 - The System.IO Namespace

Chapter 17 - Data Access with ADO.NET

PartAs youFivecan- WebseeApplicationsfrom Figureand3-17XML, theWebtypeServicesnamed Fred returns after the call as a type named Nikki:

Chapter 18 - ASP.NET Web Pages and Web Controls

Chapter

Chapter

Index

List of

List of

Figure 3-17: Passing reference types by reference allows the reference to be redirected.

The golden rule to keep in mind when passing reference types by reference is the following:

If a class type is passed by reference, the callee may change the values of the object's state data as well as the object it is referencing.

That wraps up our examination of parameter passing behavior under C#. Next up: the role of System.Array.

SOURCE The MethodsAndParams project is located under the Chapter 3 subdirectory.

CODE

C# and the .NET Platform, Second Edition

Apress © 2003 (1200 pages)

This comprehensive text starts with a brief overview of the C# language and then quickly moves to key technical and architectural issues for .NET developers.

Table of Contents

C# and the .NET Platform, Second Edition

Introduction

Part One - Introducing C# and the .NET Platform

Chapter 1 - The Philosophy of .NET

Chapter 2 - Building C# Applications

Part Two - The C# Programming Language

Chapter 3 - C# Language Fundamentals

Chapter 4 - Object-Oriented Programming with C#

Chapter 5 - Exceptions and Object Lifetime

Chapter 6 - Interfaces and Collections

Chapter 7 - Callback Interfaces, Delegates, and Events

Chapter 8 - Advanced C# Type Construction Techniques

Part Three - Programming with .NET Assemblies

Chapter 9 - Understanding .NET Assemblies

Chapter 10 - Processes, AppDomains, Contexts, and Threads

Chapter 11 - Type Reflection, Late Binding, and Attribute-Based Programming

Part Four - Leveraging the .NET Libraries

Chapter 12 - Object Serialization and the .NET Remoting Layer

Chapter 13 - Building a Better Window (Introducing Windows Forms)

Chapter 14 - A Better Painting Framework (GDI+)

Chapter 15 - Programming with Windows Forms Controls

Chapter 16 - The System.IO Namespace

Chapter 17 - Data Access with ADO.NET

Part Five - Web Applications and XML Web Services

Chapter 18 - ASP.NET Web Pages and Web Controls

Chapter 19 - ASP.NET Web Applications

Chapter 20 - XML Web Services

Index

List of Figures

List of Tables

int[] ages = {20, 22, 23, 0} ;

C# and the .NET Platform, Second Edition

Again, the curly bracketApress ©notation2003 (1200({pages)}) is simply a time saver. Therefore, the following two arrays are identical:

This comprehensive text starts with a brief overview of the

C# language and then quickly moves to key technical and

// Initialize each member at declaration...

architectural issues for .NET developers.

string[] firstNames = new string[5]{ "Steve", "Gina",

"Swallow", "Baldy", "Gunner" } ;

Table of Contents

// ...OR assign values member by member.

C# and the .NET Platform, Second Edition

string[] firstNames = new string[5];

Introduction

firstNames[0] = "Steve";

Part One - Introducing C# and the .NET Platform

firstNames[1] = "Gina";

Chapter 1 - The Philosophy of .NET firstNames[2] = "Swallow";

Chapter 2 - Building C# Applications firstNames[3] = "Baldy";

Part Two - The C# Programming Language

firstNames[4] = "Gunner";

Chapter 3 - C# Language Fundamentals

Chapter 4 - Object-Oriented Programming with C#

ChapterFinally5be -awareExc ptionsthat theandmembersObject Lifetimein a .NET array are automatically set to their respective default value.

ChapterThus, if6you- Interfhaveancesarrayand Collectionsof numerical types, each member is set to 0 (or 0.0 in the case of floating point Chaptnumerics),r 7 -arraysCallbackof Interfaces,objects beginDelegates,life set toandnull,Eventsand Boolean types are set to false.

Chapter 8 - Advanced C# Type Construction Techniques

PartArraysThree - AsProgrammingParameterswith .NET Assemblies(and Return Values)

Chapter 9 - Understanding .NET Assemblies

ChapterDeclaring10 -andProcesses,filling localAppDomains,arrays mayContexts,be helpfulandfromThreadstime to time. However, as you would hope, arrays can

Chapteralso be11passed- TypeintoReflection,and returnedLate Binding,from customand Attribufunctionse-Based. ForProgrammingexample:

Part Four - Leveraging the .NET Libraries

Chapter 12 - Object Serialization and the .NET Remoting Layer public static void PrintArray(int[] myInts)

Chapter{ 13 - Building a Better Window (Introducing Windows Forms)

Chapterfor(int14 - A Betteri =Painting0; Fra< myIntsework (GDI+).Length; i++)

Chapter 15 -ConsoleProgramming.WriteLine("Itemwith Windows Forms{0}Controlsis {1}", i, myInts[i]);

}

Chapter 16 - The System.IO Namespace

public static string[] GetStringArray()

Chapter 17 - Data Access with ADO.NET

{

Part Five - Web Applications and XML Web Services

string[] theStrings = { "Hello", "from", "GetStringArray" };

Chapter 18 - ASP.NET Web Pages and Web Controls

return theStrings;

Chapter 19 - ASP.NET Web Applications

}

Chapter 20 - XML Web Services

Index

List of Figures

Calling these static members is equally as straightforward:

List of Tables

int[] ages = {20, 22, 23, 0} ;

PrintArray(ages);

string[] strs = GetStringArray();

foreach(string s in strs)

Console.WriteLine(s);

Working with Multidimensional Arrays

In addition to the single dimension arrays you have seen thus far, C# also supports two varieties of multidimensional arrays. The first of these is termed a rectangular array. This type is simply an array of multiple dimensions, where each row is of the same length. To declare and fill a multidimensional rectangular array, proceed as follows:

Second Edition

ISBN:1590590554

with a brief overview of the

moves to key technical and

architectural issues for .NET developers.

Figure 3-19: Jagged arrays

Now that you understand how to build and populate C# arrays, you can turn your attention to the ultimate base

Table of Contents

class of any array, System.Array.

C# and the .NET Platform, Second Edition

Introduction

The System.Array Base Class

Part One - Introducing C# and the .NET Platform

Chapter 1 - The Philosophy of .NET

The most striking difference between C and C++ arrays is the fact that every array you create is automatically

Chapter 2 - Building C# Applications

derived from System.Array. This class defines a number of helpful methods that make working with arrays

Let's see some of these members in action. The following code makes use of the static Reverse() and Clear() methods (and the Length property) to pump out some information about the firstName string array to the console:

// Create some string arrays and exercise some System.Array members.

class Arrays

{

public static int Main(string[] args)

{

// Array of strings.

C# and the .NET Platform, Second Edition

string[] firstNames = new string[5]{ "Steve", "Gina", "Swallow",

Apress © 2003 (1200 pages)

// Print out names in declared order.

This compWriteLine("Hereehensive text starts with a brief overview of the

Console. is the array:");

C# language and then quickly moves to key technical and for(int i = 0; i < firstNames.Length; i++)

architectural issues for .NET developers.

Console.Write(firstNames[i] + "\t");

// Flip things around using the static Reverse() method...

Array.Reverse(firstNames);

Table of Contents

// ... and print them.

C# and the .NET Platform, Second Edition

Console.WriteLine("Here is the array once reversed:");

Introduction

for(int i = 0; i < firstNames.Length; i++)

Console.Write(firstNames[i] + "\t");

Chapter 1 - The Philosophy of .NET

// Clear out all but young gunner.

Chapter 2 - Building C# Applications

Console.WriteLine("Cleared out all but young Gunner...");

Part Two - The C# Programming Language

Array.Clear(firstNames, 1, 4);

Chapter 3 - C# Language Fundamentals

for(int i = 0; i < firstNames.Length; i++)

Chapter 4 - Object-Oriented Programming with C#

Console.Write(firstNames[i] + "\t\n");

Chapter 5 - Exceptions and Object Lifetime

return 0;

Chapter 6 - Interfaces and Collections

}

Chapter} 7 - Callback Interfaces, Delegates, and Events

Chapter 8 - Advanced C# Type Construction Techniques

Part Three - Programming with .NET Assemblies

Chapter

Figure 3-20: Fun with System.Array

Chapter 17 - Data Access with ADO.NET

Part Five - Web Applications and XML Web Services

SOURCE The Arrays application is located under the Chapter 3 subdirectory.

Chapter 18 - ASP.NET Web Pages and Web Controls

CODE

Chapter 19 - ASP.NET Web Applications

Chapter 20 - XML Web Services

Index

List of Figures

List of Tables

String ManipulationC# and the .NETin Platform,C# Second Edition

As you have already seen, string is a keyword type in C#. However, like all intrinsic types, string actually

Apress © 2003 (1200 pages)

aliases a type in the .NET library, which in this case is a class named System.String. System.String provides a

This comprehensive text starts with a brief overview of the

number of methodsC# youlanguagewouldandexpectthenfromquicklysuchmovesa utilityto keyclass,techincludingical a d methods that return the length, find substrings, convertarchitecturalto and fromissuppercase/lowercase,es for .NET developersand. so forth. Table 3-11 lists some (but by no means all) of the interesting members.

You should be aware of a few aspects of C# string manipulation. First, although string is a reference type, the

Part Five - Web Applications and XML Web Services

equality operators (== and !=) are defined to compare the values of string objects, not the memory to which

Chapter 18 - ASP.NET Web Pages and Web Controls

they refer. On a related note, understand that the addition operator (+) has been overloaded as a shorthand

Chapter 19 - ASP.NET Web Applications

alternative to calling Concat():

Chapter 20 - XML Web Services

Index

// == and != are used to compare the values within strings.

List of Figures

// + is used for concatenation.

List of Tables

public static int Main(string[] args)

{

// Alternative ways to declare a string.

System.String strObj = "This is a TEST";

string s = "This is another TEST";

// Test for equality between the stings.

if(s == strObj)

Console.WriteLine("Same info...");

else

Console.WriteLine("Not the same info...");

// Concatenation.

string newString = s + strObj; Console.WriteLine("s + strObj = {0} ", newString);

//System.String also defines a custom indexer to access each

//character in the string.

string finalString = @"\n\tString file: 'C:\CSharpProjects\Strings\string.cs'";

C# and the .NET Platform, Second Edition

Console.WriteLine(finalString);

The output has beenThis prefixedcomprehensivewith "\n\t",text asstartsthesewithescapea bri fcharactersoverview ofarethenot processed in @-quoted strings. Also note that verbatimC# languagestringsandcanthenbe usedquicklytomovesignoretowhitekeyspacetechnicalthatandflows over multiple lines. Assume you

architectural issues for .NET developers.

have a mighty long string literal that would require the reader to scroll right for a rather long time. If you were to make use of @-prefixed strings, you would be able to author the following (more readable) code:

Table of Contents

// White Space is preserved!

C# and the .NET Platform, Second Edition

string myLongString = @"Stuff Stuff Stuff Stuff Stuff

Introduction

Stuff Stuff Stuff Stuff Stuff Stuff Stuff

Part One - Introducing C# and the .NET Platform

Stuff Stuff Stuff Stuff Stuff";

Chapter 1 - The Philosophy of .NET

Console.WriteLine(myLongString);

Chapter 2 - Building C# Applications

Part Two - The C# Programming Language

Chapter 3 - C# Language Fundamentals

Using System.Text.StringBuilder

Chapter 4 - Object-Oriented Programming with C#

Chapter 5 - Exceptions and Object Lifetime

One thing to be very aware of with regard to C# strings: The value of a string cannot be modified once

Chapter 6 - Interfaces and Collections

established. Like Java, C# strings are immutable. In fact, if you examine the methods of System.String, you

Chapter 7 - Callback Interfaces, Delegates, and Events

notice that the methods that seem to internally modify a string, in fact return a modified copy of the string. For

Chapter 8 - Advanced C# Type Construction Techniques

example, when you send the ToUpper() message to a string object, you are not modifying the underlying

Part Three - Programming with .NET Assemblies

buffer of the existing string object, but are returned a fresh copy of the buffer in uppercase form:

Chapter 9 - Understanding .NET Assemblies

Chapter 10 - Processes, AppDomains, Contexts, and Threads

// Make changes to this string? Not really...

Chapter 11 - Type Reflection, Late Binding, and Attribute-Based Programming

System.String strFixed = "This is how I began life";

Part Four - Leveraging the .NET Libraries

Console.WriteLine(strFixed);

Chapter 12 - Object Serialization and the .NET Remoting Layer

// Returns an uppercase copy of strFixed.

Chapter 13 - Building a Better Window (Introducing Windows Forms) string upperVersion = strFixed.ToUpper();

Chapter 14 - A Better Painting Framework (GDI+)

Console.WriteLine(strFixed);

Chapter 15 - Programming with Windows Forms Controls

Console.WriteLine(upperVersion);

Chapter 16 - The System.IO Namespace

Chapter 17 - Data Access with ADO.NET

It can become slightly annoying (and inefficient) to work with copies of copies of strings. To help ease the pain,

Part Five - Web Applications and XML Web Services

the System.Text namespace defines a class named StringBuilder. This class operates much more like an

Chapter 18 - ASP.NET Web Pages and Web Controls

public static int Main(string[] args)

{

// Create a StringBuilder and change the underlying buffer.

StringBuilder myBuffer = new StringBuilder("I am a buffer");

myBuffer.Append(" that just got longer...");

Console.WriteLine(myBuffer);

return 0;

}

}

Beyond appending to your internal buffer, the StringBuilder class allows you to replace and remove characters at will. Once you have established the state of your buffer, call ToString() to store the final result into a System.String data type:

C# and the .NET Platform, Second Edition using System;

public static int Main(string[] args) architectural issues for .NET developers.

{

StringBuilder myBuffer = new StringBuilder("I am a buffer");

myBuffer.Append(" that just got longer...");

Table of Contents

Console.WriteLine(myBuffer);

C# and the .NET Platform, Second Edition

myBuffer.Append("and even longer.");

Introduction

Console.WriteLine(myBuffer);

Part One - Introducing C# and the .NET Platform

// Transfer the buffer to an uppercase fixed string.

Chapter 1 - The Philosophy of .NET

string theReallyFinalString = myBuffer.ToString().ToUpper();

Chapter 2 - Building C# Applications

Console.WriteLine(theReallyFinalString);

Part Two - The C# Programming Language

return 0;

Chapter 3 - C# Language Fundamentals

}

Chapter 4 - Object-Oriented Programming with C#

}

Chapter 5 - Exceptions and Object Lifetime Chapter 6 - Interfaces and Collections

Chapter 7 - Callback Interfaces, Delegates, and Events

ChapterNow, do8 understand- AdvancedthatC# inTypemanyConstructioncases, SystemTechniques.String will be your textual object of choice. For most

Papplications,rt Three - Programmingthe overheadwithassociated.NET Assembliwith returnings modified copies of character data will be negligible. ChaptHowever,r 9 if- youUnderstandingare building.NETa textAssemblies-intensive application (such as a word processor application) you will most

likely find that using System.Text.StringBuilder will improve performance. As you might assume, StringBuilder

Chapter 10 - Processes, AppDomains, Contexts, and Threads

contains additional methods and properties beyond those examined here. I leave it to you to drill into more

Chapter 11 - Type Reflection, Late Binding, and Attribute-Based Programming

specifics at your leisure.

Part Four - Leveraging the .NET Libraries

Chapter 12 - Object Serialization and the .NET Remoting Layer

SOURCE The Strings project is located under the Chapter 3 subdirectory.

Chapter 13 - Building a Better Window (Introducing Windows Forms)

CODE

Chapter 14 - A Better Painting Framework (GDI+)

Chapter 15 - Programming with Windows Forms Controls

Chapter 16 - The System.IO Namespace

Chapter 17 - Data Access with ADO.NET

Part Five - Web Applications and XML Web Services

Chapter 18 - ASP.NET Web Pages and Web Controls

Chapter 19 - ASP.NET Web Applications

Chapter 20 - XML Web Services

Index

List of Figures

List of Tables