Visual Basic 2008编程高级教程

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"Advanced Programming Using Visual Basic 2008" 是一本由微软资深专家撰写的专业书籍，主要讲解如何利用Visual Basic 2008进行高级编程。该书由McGraw-Hill Primis出版社于2010年出版，是针对VB .NET 2008、ASP、ASP.NET和C#等技术的权威参考资料。在这本书中，作者深入浅出地介绍了Visual Basic 2008的关键概念和技术。首先，读者将学习到Visual Basic的基础知识，包括语言语法、变量、数据类型、控制结构（如条件语句和循环）以及函数的使用。这些基础知识对于任何编程学习者都是至关重要的，它们构成了编写程序的基石。随着内容的深入，书中会详细讨论面向对象编程（OOP）的概念，这是Visual Basic 2008的核心特性之一。读者将学习类、对象、属性、方法和继承等OOP概念，并通过实例来理解如何在VB 2008中实现这些概念。此外，书中还会介绍事件驱动编程，这是GUI应用程序开发中的关键部分，比如Windows Forms的应用。在Web开发方面，本书涵盖了ASP.NET技术，让读者了解如何使用VB 2008创建动态网页。这包括服务器控件、页面生命周期、状态管理以及与数据库的交互。ASP.NET MVC框架可能会被提及，它是ASP.NET的一个重要扩展，允许开发者采用模型-视图-控制器架构来构建Web应用。此外，书中还会讨论数据库编程，包括ADO.NET库的使用，如连接数据库、执行SQL查询、处理结果集以及数据绑定。这将帮助读者理解如何在VB 2008中实现数据驱动的应用程序。最后，书中的实践项目和示例代码将帮助读者巩固所学知识，提高编程技能。此外，可能还会有调试技巧、错误处理和性能优化等方面的指导，这些都是成为专业程序员不可或缺的部分。《Advanced Programming Using Visual Basic 2008》是一本全面覆盖VB 2008及其相关技术的教材，适合初学者和有一定经验的开发者，它提供了丰富的实例和实践建议，有助于读者深入理解和掌握Visual Basic 2008的高级编程技巧。

Bradley−Millspaugh:

Advanced Programming

Using Visual Basic 2008

1. Visual Studio and the

.NET Framework

Text

Companies, 2010

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CHAPTER

Visual Studio and the

.NET Framework

at the completion of this chapter, you will be able to . . .

1. Distinguish the features of the Visual Studio IDE and the .NET Framework.

2. Identify and understand the purpose of each of the files listed in the Solution Explorer.

3. Understand what happens at compile time.

4. Set and display data from the application’s assembly attributes.

5. Create an MDI project with a parent form, child forms, a toolbar, status bar, context menus,

and ToolTips.

6. Use the singleton design pattern to create a class that should be instantiated only once.

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2 ADVANCED PROGRAMMING USING VISUAL BASIC 2008 Visual Studio and the .NET Framework

Microsoft revolutionized the programming for Windows applications and be-

came a bigger player in the development of Web applications with the introduc-

tion of the .NET Framework and Visual Studio (VS). These products introduced

significant changes into program development for Visual Basic (VB). Not only

did .NET bring true object orientation to the language; it also provided great

advances in the ease of developing projects for cross-platform compatibility.

The two major parts of .NET are the Microsoft .NET Framework and the

Visual Studio integrated development environment (IDE). The IDE is used to

develop programs and the Framework runs the programs.

The .NET Framework

The .NET Framework provides a platform for developing and running applica-

tions and Windows Communications Foundation (WCF) services written in mul-

tiple languages on multiple platforms. The Framework is composed of the common

language runtime, class libraries, and ASP.NET—a component-based version of

active server pages (ASP).

The Common Language Runtime

The common language runtime (CLR) is an environment that manages

execution of code. It provides services for tasks such as integrating com ponents

developed in different languages, handling errors across languages, providing

security, and managing the storage and destruction of objects.

Any code that is compiled to run in the CLR is called managed code .

The managed code automatically contains metadata , which means data that

describe data . A common language runtime portable executable (PE) file con-

tains the metadata along with the code. The metadata include data types, mem-

bers, references, and information needed to load classes and to call methods

from a class.

The CLR also manages memory used by .NET applications. Objects that

are no longer being used are automatically removed from memory by the gar-

bage collector component of the CLR. When you allow the runtime to handle

the garbage collection of objects, the data are referred to as managed data .

Although you can manage application memory yourself, it is usually better and

more secure to let the runtime handle it.

Your code can be integrated with classes and methods of managed code

written in other programming languages. The CLR has standards for data types

that allow you to pass an instance of one of your classes to a method created in

a different language. Although we will not be doing any cross-language pro-

gramming in this text, you should be aware of this powerful feature. Note that it

is also possible to integrate methods and components created in unmanaged

code, but beware of calling unmanaged code such as C++ functions or COM

components as they may introduce security risks to your program.

The Class Library

All of the .NET classes and interfaces are stored in a library known as the

.NET Framework class library . The library is organized into sections or

groups known as namespaces . You should be familiar with some of the common

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CHAPTER 1 3

namespaces such as System and System.Drawing . Each namespace contains

classes, structures, enumerations, delegates, and/or interfaces that you can use

in your programs. Table 1.1 shows some of the namespaces in the .NET Frame-

work class library.

Selected Namespaces from the .NET Class Library

Table 1. 1

Namespace Contents

System Base classes and fundamental classes for data types,

events, and event handlers.

System.Collections Definitions of collections of objects such as lists,

queues, and dictionaries.

System.Data ADO.NET architecture used to access databases.

System.Drawing GDI+ graphics for drawing on the screen, printer, or

any other graphic device.

System.IO Types for reading and writing data streams and files.

System.Linq Supports queries for Language-Integerated Queries

System.Security Base classes for permissions.

System.Threading Classes for multithreaded programming.

System.Web.Services Classes for building and using Web Services.

System.Windows.Forms Classes for creating graphical components for programs

that execute in the Windows operating environment.

System.XML Support for XML processing. XML is a standard for

transferring data.

The classes in the library comply with published standards known as the

Common Language Specification (CLS) . The CLS specifies how a lan-

guage that interacts with the CLR should behave. If you want a program to in-

teract with programs and components written in other languages, you should

make sure that it is CLS compliant. The rules for CLS compliance can be found

in the .NET Framework Developer’s Guide under the heading “Writing CLS-

Compliant Code.” Note that all VB programs that you write using the VS IDE

will be CLS compliant automatically.

Types

The .NET documentation uses the general term types to refer to the classes,

structures, enumerations, delegates, interfaces, and data types in the library, as

well as any that you define. You can think of a type as any element that you can

use in the

As clause of a declaration:

Dim AnyName As SomeType

Value Types versus Reference Types

When you declare a variable, it may be considered a value type or a refer-

ence type . The difference between the two determines how the runtime will

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4 ADVANCED PROGRAMMING USING VISUAL BASIC 2008 Visual Studio and the .NET Framework

treat the variables when you assign one variable to another. For example, if you

assign one integer variable to another, you have two memory locations with the

same value:

SecondValueInteger = FirstValueInteger

However, if you assign one reference type to another, you have two variables

that point to the same object in memory:

SecondForm = FirstForm ' Assign reference for first form to second form.

Any changes that you make to either variable are made to the one object in

memory to which both variables refer. In some previous versions of VB, refer-

ence types were called object variables . However, VB reference types include

more types than the more restrictive object variables.

' Value types.

Dim FirstValueInteger As Integer = 10

Dim SecondValueInteger As Integer

SecondValueInteger = FirstValueInteger

FirstValueInteger = 5

' What is the value in each of the variables?

Debug.WriteLine("FirstValueInteger = " & FirstValueInteger.ToString() & _

"; SecondValueInteger = " & SecondValueInteger.ToString())

' Reference types.

Dim FirstForm As New Form1()

Dim SecondForm As Form1

SecondForm = FirstForm ' Assign reference for first form to second form.

SecondForm.Text = "Second Form Caption"

FirstForm.Text = "New Caption for First Form"

' What is the Text property of FirstForm? Of SecondForm?

Debug.WriteLine("FirstForm = " & FirstForm.Text & _

"; SecondForm = " & SecondForm.Text)

Can you predict the debug output from the two groups of statements above?

Follow the logic and write down your answer; then look back here to check

your understanding.

FirstValueInteger = 5; SecondValueInteger = 10

FirstForm = New Caption for First Form; SecondForm = New Caption for First Form

All numeric data types are value types. Reference types include class types,

arrays (even if the individual elements are numeric), and strings. A value type

always holds a value; when you declare a new variable of a value type, the vari-

able is always initialized, either to a value that you supply or to the default value.

A reference type may or may not hold a value; you can use the

IsNot Nothing

condition to determine whether the variable refers to an instance of an object.

Compiling to Intermediate Language

The program code that you write is referred to as source code . The compiler

translates your code into Microsoft intermediate language (MSIL) o r

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sometimes referred to as just IL . MSIL is a platform-independent set of in-

structions that is combined with the metadata to form a file called a portable

executable (PE) file, which has an .exe or .dll extension. When your program

runs, the MSIL is converted to the native code of the specific machine only

as it is needed, using a just-in-time (JIT) compiler, which is part of the CLR

( Figure 1.1 ).

F i gure 1. 1

The steps in compiling and

executing a program using the

.NET CLR.

Native code

for target

computer

Managed

source

code

CLS

compliant

language

compiler

JIT

compiler

MSIL and

Metadata

Assemblies

An assembly is a basic unit of code that may be a single PE file or multiple

files. Each of your applications will be contained in a single assembly, which

is the smallest deployable piece of code. An assembly has an assembly man-

ifest that contains metadata about the version, a table describing all of the

files needed by the assembly, and an “assembly reference list” that specifies

all of the external files needed, such as DLLs created by someone else. An

assembly is similar to an .exe or a .dll file written in earlier versions of Visual

Basic—it contains all of the necessary information to run the application or

component.

Recall that the .NET Framework class library is not one big file but

rather a collection of files. The classes are stored in many files with the ex-

tension .dll and referred to as DLLs (for dynamic link libraries). Each of the

DLLs in the class library is one assembly. As your program begins execu-

tion, only the needed assemblies are loaded into memory. When you want to

use a type that is not already referenced, you must add a reference to the

DLL (assembly).

Attributes

Attributes are tags containing information about parts of a program such as

types or methods. The system defines many attributes of your assembly, such

as the name, version, culture, and security. The attributes are part of the meta-

data in a .NET assembly. The process of examining the metadata in an assem-

bly’s attributes is called reflection .

Later in this chapter, you will learn to retrieve and use the custom attri-

butes in a project’s assembly information, which is stored in the Assembly-

Info.vb file.

The References Collection

A reference object is used to connect a Visual Basic project to external com-

ponents. The two types of reference objects are assemblies and COM objects.

A reference to another project is an assembly reference and is called a project-

to-project reference . COM objects are components written in versions of VB

prior to .NET, or other non-CLS-compliant languages.

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