vb.net泛型委托 泛型报错

VB6与VB.NET的差异有哪些？

.Net平台引入了很多先进vb.net泛型委托的技术，导致了VB6和VB.Net之间产生了一个巨大的鸿沟

就语言功能上来讲，VB.net完全是为了.Net技术而生，具有更好的运行效率和更加强大的功能（某些方面甚至超过了C#)

从语法角度上来讲，VB.net成为了真正的OOP(面向对象语言），不但支持类的继承、派生，还支持委托、泛型等等更加高级的编程技术

如果vb.net泛型委托你是从VB6升级到.net的话，建议要将VB.net当作一门新的语言来学。以VB6的经验来应用到VB.net上是会犯很多错误的

关于从VB6升级到VB.net的代码变换问题，注意以下几个重要的要点即可vb.net泛型委托：

1.不再支持Load、Shell、.LoadPicture等语句

请用相关的.net语句替换

2.String类为引用类，也就是说

Dim s1,s2 as String

s1="FFFFFFF"

s2=s1

此时修改s2的值s1也会跟着相应变化

3.不再支持Variant型和Currency型变量

分别用Object和Demical类型代替

4.变量长度的变化：

VB6的byte、Integer、long型分别被vb.net的byte、short、integer代替，而long型则成为64位大小的整数。新增了UInteger、ULong、SByte等无符号整数类型

相关问答

Q1: vb.net高手请帮帮我看看下面这代码什么意思，详解哦，先谢了，Handles 作用是什么

在VB.Net当中,事件的"关联"是需要明显标志的,不像vb6当中,声明一个过程就是事件执行过程vb.net泛型委托了

Handles用来静态"关联"一个或多个事件到一个过程

"关联"时,过程的签名必须与事件的签名相同(签名的意义请查看相关文档)

在VB.Net当中,事件也是一个对象(VB.Net当中一切皆为对象)

使用Handles时实际就相当于创建vb.net泛型委托了一个对委托的实现(委托的意义请查看相关文档)

可以简单的认为,当事件被触发时,被Handles"关联"了的那些过程代码将被执行

而且,被"关联"的过程可以任意起名,不需要与事件和对象的名称相对应

上述代码如果去掉Handles 及其后面的内容,它将是一个最普通不过的过程,与其它过程没有两样,也不会有任何事件被触发时去执行这段代码,正因为加入了Handles 及其后面的一堆事件,它才会因事件被触发而被执行

说得再简单一点: 当PictureBox1.DoubleClick, PictureBox4.DoubleClick, PictureBox3.DoubleClick,PictureBox2.DoubleClick当中的任何一个事件被触发时,上述这个过程的代码都将被执行

再说说参数: sender表示触发了此事件的对象,在这里就是PictureBox1/PictureBox2/PictureBox3/PictureBox4当中的某一个,利用它能知道到底是哪个对象触发了此事件,e在这里没有用处,利用不到什么,之所以有它,是因为Object/EventArgs是.Net事件的基本签名方式,它的好处在vb.net泛型委托你以后对.Net深入之后能体会到.

这些参数的值都是通过被触发的事件传递过来的,可以简单的认为[事件调用了此过程并为参数赋了值]

Q2: vb.net中如何用事件和委托，会C#中的事件和委托，但不知VB.net中的语法，望给个简单的例子熟悉语法。

一委托：此示例演示如何将方法与委托关联然后通过委托调用该方法。

创建委托和匹配过程

创建一个名为 MySubDelegate 的委托。

Delegate Sub MySubDelegate(ByVal x As Integer)

声明一个类vb.net泛型委托，该类包含与该委托具有相同签名的方法。

Class class1

Sub Sub1(ByVal x As Integer)

MsgBox("The value of x is: " CStr(x))

End Sub

End Class

定义一个方法vb.net泛型委托，该方法创建该委托的实例并通过调用内置的 Invoke 方法调用与该委托关联的方法。

Protected Sub DelegateTest()

Dim c1 As New class1

' Create an instance of the delegate.

Dim msd As MySubDelegate = AddressOf c1.Sub1

' Call the method.

msd.Invoke(10)

End Sub

二、事件

下面的示例程序阐释如何在一个类中引发一个事件vb.net泛型委托，然后在另一个类中处理该事件。AlarmClock 类定义公共事件 Alarm，并提供引发该事件的方法。AlarmEventArgs 类派生自 EventArgs，并定义 Alarm 事件特定的数据。WakeMeUp 类定义处理 Alarm 事件的 AlarmRang 方法。AlarmDriver 类一起使用类，将使用 WakeMeUp 的 AlarmRang 方法设置为处理 AlarmClock 的 Alarm 事件。

该示例程序使用事件和委托和引发事件中详细说明的概念。

示例

' EventSample.vb.

'

Option Explicit

Option Strict

Imports System

Imports System.ComponentModel

Imports Microsoft.VisualBasic

Namespace EventSample

' Class that contains the data for

' the alarm event. Derives from System.EventArgs.

'

Public Class AlarmEventArgs

Inherits EventArgs

Private _snoozePressed As Boolean

Private nrings As Integer

'Constructor.

'

Public Sub New(snoozePressed As Boolean, nrings As Integer)

Me._snoozePressed = snoozePressed

Me.nrings = nrings

End Sub

' The NumRings property returns the number of rings

' that the alarm clock has sounded when the alarm event

' is generated.

'

Public ReadOnly Property NumRings() As Integer

Get

Return nrings

End Get

End Property

' The SnoozePressed property indicates whether the snooze

' button is pressed on the alarm when the alarm event is generated.

'

Public ReadOnly Property SnoozePressed() As Boolean

Get

Return _snoozePressed

End Get

End Property

' The AlarmText property that contains the wake-up message.

'

Public ReadOnly Property AlarmText() As String

Get

If _snoozePressed Then

Return "Wake Up!!! Snooze time is over."

Else

Return "Wake Up!"

End If

End Get

End Property

End Class

' Delegate declaration.

'

Public Delegate Sub AlarmEventHandler(sender As Object, _

e As AlarmEventArgs)

' The Alarm class that raises the alarm event.

'

Public Class AlarmClock

Private _snoozePressed As Boolean = False

Private nrings As Integer = 0

Private stopFlag As Boolean = False

' The Stop property indicates whether the

' alarm should be turned off.

'

Public Property [Stop]() As Boolean

Get

Return stopFlag

End Get

Set

stopFlag = value

End Set

End Property

' The SnoozePressed property indicates whether the snooze

' button is pressed on the alarm when the alarm event is generated.

'

Public Property SnoozePressed() As Boolean

Get

Return _snoozePressed

End Get

Set

_snoozePressed = value

End Set

End Property

' The event member that is of type AlarmEventHandler.

'

Public Event Alarm As AlarmEventHandler

' The protected OnAlarm method raises the event by invoking

' the delegates. The sender is always this, the current instance

' of the class.

'

Protected Overridable Sub OnAlarm(e As AlarmEventArgs)

RaiseEvent Alarm(Me, e)

End Sub

' This alarm clock does not have

' a user interface.

' To simulate the alarm mechanism it has a loop

' that raises the alarm event at every iteration

' with a time delay of 300 milliseconds,

' if snooze is not pressed. If snooze is pressed,

' the time delay is 1000 milliseconds.

'

Public Sub Start()

Do

nrings += 1

If stopFlag Then

Exit Do

Else

If _snoozePressed Then

System.Threading.Thread.Sleep(1000)

If (True) Then

Dim e As New AlarmEventArgs(_snoozePressed, nrings)

OnAlarm(e)

End If

Else

System.Threading.Thread.Sleep(300)

Dim e As New AlarmEventArgs(_snoozePressed, nrings)

OnAlarm(e)

End If

End If

Loop

End Sub

End Class

' The WakeMeUp class has a method AlarmRang that handles the

' alarm event.

'

Public Class WakeMeUp

Public Sub AlarmRang(sender As Object, e As AlarmEventArgs)

Console.WriteLine((e.AlarmText + ControlChars.Cr))

If Not e.SnoozePressed Then

If e.NumRings Mod 10 = 0 Then

Console.WriteLine(" Let alarm ring? Enter Y")

Console.WriteLine(" Press Snooze? Enter N")

Console.WriteLine(" Stop Alarm? Enter Q")

Dim input As String = Console.ReadLine()

If input.Equals("Y") Or input.Equals("y") Then

Return

Else

If input.Equals("N") Or input.Equals("n") Then

CType(sender, AlarmClock).SnoozePressed = True

Return

Else

CType(sender, AlarmClock).Stop = True

Return

End If

End If

End If

Else

Console.WriteLine(" Let alarm ring? Enter Y")

Console.WriteLine(" Stop Alarm? Enter Q")

Dim input As String = Console.ReadLine()

If input.Equals("Y") Or input.Equals("y") Then

Return

Else

CType(sender, AlarmClock).Stop = True

Return

End If

End If

End Sub

End Class

' The driver class that hooks up the event handling method of

' WakeMeUp to the alarm event of an Alarm object using a delegate.

' In a forms-based application, the driver class is the

' form.

'

Public Class AlarmDriver

Public Shared Sub Main()

' Instantiates the event receiver.

Dim w As New WakeMeUp()

' Instantiates the event source.

Dim clock As New AlarmClock()

' Wires the AlarmRang method to the Alarm event.

AddHandler clock.Alarm, AddressOf w.AlarmRang

clock.Start()

End Sub

End Class

End Namespace

Q3: vb.net 中在模块（module）里如何实现委托

委托三个步骤

1、声明委托 用Delegate 声明一个委托 类型 参数要和 被委托的方法一样 例如 Delegate Function a(byval x as string) as string

2、实例化委托 dim t as new a(AddressOf Function Name)

3.通过 t(参数) 或者 t.Invoke(参数调用委托)

示例：

Module module1

Delegate Function a(ByVal x As Integer, ByVal y As Integer) As Integer '声明委托类型 委托可以使一个对象调用另一个对象的方法

Function sum(ByVal x As Integer, ByVal y As Integer) As Integer

Return (x + y)

End Function

Sub main()

Dim d As New a(AddressOf sum) '实例化委托

Dim s = 0

s = d.Invoke(1, 2) '执行委托

Console.WriteLine(s.ToString())

s = d(1, 2) '执行委托

Console.WriteLine(s.ToString())

MsgBox("")

End Sub

End Module

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