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可支持语言
Microsoft .NET Platform 目前提供对以下三种语言的内置支持：C#、Visual Basic 和 JScript。
本教程中的练习和代码示例展示如何使用 C#、Visual Basic 和 JScript 生成 .NET 应用程序。有关其他语言语法的信息，请参考
.NET 框架 SDK 的完整文档。
提供下表以帮助您理解本教程中的代码示例以及三种语言之间的差异：
变量声明
Dim x As Integer
Dim s As String
Dim s1, s2 As String
Dim o 'Implicitly Object
Dim obj As New Object()
Public name As String |
语句
注释
| ' This is a comment
' This
' is
' a
' multiline
' comment
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访问索引属性
Dim s, value As String
s = Request.QueryString("Name")
value = Request.Cookies("Key").Value
'Note that default non-indexed properties
'must be explicitly named in VB
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声明索引属性
' Default Indexed Property
Public Default ReadOnly Property DefaultProperty(Name As String)
As String
Get
Return CStr(lookuptable(name))
End Get
End Property |
声明简单属性
| Public Property Name As String
Get
...
Return ...
End Get
Set
... = Value
End Set
End Property
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声明和使用枚举
' Declare the Enumeration
Public Enum MessageSize
Small = 0
Medium = 1
Large = 2
End Enum
' Create a Field or Property
Public MsgSize As MessageSize
' Assign to the property using the Enumeration
values
MsgSize = small
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枚举集合
Dim S As String
For Each S In Coll
...
Next |
声明和使用方法
' Declare a void return function
Sub VoidFunction()
...
End Sub
' Declare a function that returns a
value
Function StringFunction() As String
...
Return CStr(val)
End Function
' Declare a function that takes and
returns values
Function ParmFunction(a As String, b As String) As String
...
Return CStr(A & B)
End Function
' Use the Functions
VoidFunction()
Dim s1 As String = StringFunction()
Dim s2 As String = ParmFunction("Hello", "World!")
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自定义属性
' Stand-alone attribute
<STAThread>
' Attribute with parameters
<DllImport("ADVAPI32.DLL")>
' Attribute with named parameters
<DllImport("KERNEL32.DLL", CharSet:=CharSet.Auto)>
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数组
Dim a(2) As String
a(0) = "1"
a(1) = "2"
a(2) = "3"
Dim a(2,2) As String
a(0,0) = "1"
a(1,0) = "2"
a(2,0) = "3"
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初始化
Dim s As String = "Hello
World"
Dim i As Integer = 1
Dim a() As Double = { 3.00, 4.00, 5.00 } |
If 语句
If Not (Request.QueryString
= Nothing)
...
End If |
Case 语句
Select Case FirstName
Case "John"
...
Case "Paul"
...
Case "Ringo"
...
Case Else
...
End Select |
For 循环
Dim I As Integer
For I = 0 To 2
a(I) = "test"
Next |
While 循环
Dim I As Integer
I = 0
Do While I < 3
Console.WriteLine(I.ToString())
I += 1
Loop |
异常处理
Try
' Code that throws exceptions
Catch E As OverflowException
' Catch a specific exception
Catch E As Exception
' Catch the generic exceptions
Finally
' Execute some cleanup code
End Try |
字符串连接
' Using Strings
Dim s1, s2 As String
s2 = "hello"
s2 &= " world"
s1 = s2 & " !!!"
' Using StringBuilder class for performance
Dim s3 As New StringBuilder()
s3.Append("hello")
s3.Append(" world")
s3.Append(" !!!")
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事件处理程序委托
Sub MyButton_Click(Sender
As Object,
E As EventArgs)
...
End Sub |
声明事件
' Create a public event
Public Event MyEvent(Sender as Object, E as EventArgs)
' Create a method for firing the event
Protected Sub OnMyEvent(E As EventArgs)
RaiseEvent MyEvent(Me, E)
End Sub
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向事件添加事件处理程序或从事件移除事件处理程序
AddHandler Control.Change,
AddressOf Me.ChangeEventHandler
RemoveHandler Control.Change, AddressOf Me.ChangeEventHandler |
强制类型转换
Dim obj As MyObject
Dim iObj As IMyObject
obj = Session("Some Value")
iObj = CType(obj, IMyObject) |
转换
Dim i As Integer
Dim s As String
Dim d As Double
i = 3
s = i.ToString()
d = CDbl(s)
' See also CDbl(...), CStr(...), ...
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带继承的类定义
| Imports System
Namespace MySpace
Public Class Foo : Inherits Bar
Dim x As Integer
Public Sub New()
MyBase.New()
x = 4
End Sub
Public Sub Add(x As Integer)
Me.x = Me.x + x
End Sub
Overrides Public Function GetNum()
As Integer
Return x
End Function
End Class
End Namespace
' vbc /out:libraryvb.dll /t:library
' library.vb
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实现接口
Public Class MyClass : Implements
IEnumerable
...
Function IEnumerable_GetEnumerator()
As IEnumerator Implements IEnumerable.GetEnumerator
...
End Function
End Class
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带 Main 方法的类定义
| Imports System
Public Class ConsoleVB
Public Sub New()
MyBase.New()
Console.WriteLine("Object Created")
End Sub
Public Shared Sub Main()
Console.WriteLine("Hello World")
Dim cvb As New ConsoleVB
End Sub
End Class
' vbc /out:consolevb.exe /t:exe console.vb
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标准模块
| Imports System
Public Module ConsoleVB
Public Sub Main()
Console.WriteLine("Hello World")
End Sub
End Module
' vbc /out:consolevb.exe /t:exe console.vb
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感谢2001 Microsoft Corporation教材提供 |
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