如何在VB.NET中编写事件处理程序?
我试图在VB.NET中测试非常简单的事件处理 到目前为止,我已经:如何在VB.NET中编写事件处理程序?,.net,vb.net,events,event-handling,visual-studio-2005,.net,Vb.net,Events,Event Handling,Visual Studio 2005,我试图在VB.NET中测试非常简单的事件处理 到目前为止,我已经: Public Delegate Sub TestEventDelegate() Public Event TestEvent As TestEventDelegate Sub MySub Raise TestEvent End Sub 如何为刚刚显示简单的消息框的上述事件编写事件处理程序 在VB中,我们有两种方法订阅Publisher类的事件 'Delegate Public Delegate Sub TestEve
Public Delegate Sub TestEventDelegate()
Public Event TestEvent As TestEventDelegate
Sub MySub
Raise TestEvent
End Sub
如何为刚刚显示简单的
消息框的上述事件编写事件处理程序 在VB中,我们有两种方法订阅Publisher
类的事件
'Delegate
Public Delegate Sub TestEventDelegate()
'Event publisher class that publishes and raises an event
Public Class EventPublisher
Private _num As Integer
Public Event NumberChanged As TestEventDelegate
Public Property Number As Integer
Get
Return _num
End Get
Set(value As Integer)
_num = value
RaiseEvent NumberChanged()
End Set
End Property
End Class
'Event subscriber class
Public Class EventSubscriber
'instance of EventPublisher class
Private WithEvents myObject As New EventPublisher
'Handler of myObject.NumberChanged event
Public Sub ShowMessage() Handles myObject.NumberChanged
Console.WriteLine("Value has been changed")
End Sub
Shared Sub Main()
Dim es As New EventSubscriber
es.myObject.Number = 10
es.myObject.Number = 20
'Handle the events dynamically using AddHandler
Dim ep1 As New EventPublisher
ep1.Number = 101
'Attach an event to the handler
AddHandler ep1.NumberChanged, AddressOf TestIt
ep1.Number = 102
End Sub
Shared Sub TestIt()
Console.WriteLine("Number is modified")
End Sub
End Class
在VB中,我们有两种方法来订阅Publisher
类的事件
'Delegate
Public Delegate Sub TestEventDelegate()
'Event publisher class that publishes and raises an event
Public Class EventPublisher
Private _num As Integer
Public Event NumberChanged As TestEventDelegate
Public Property Number As Integer
Get
Return _num
End Get
Set(value As Integer)
_num = value
RaiseEvent NumberChanged()
End Set
End Property
End Class
'Event subscriber class
Public Class EventSubscriber
'instance of EventPublisher class
Private WithEvents myObject As New EventPublisher
'Handler of myObject.NumberChanged event
Public Sub ShowMessage() Handles myObject.NumberChanged
Console.WriteLine("Value has been changed")
End Sub
Shared Sub Main()
Dim es As New EventSubscriber
es.myObject.Number = 10
es.myObject.Number = 20
'Handle the events dynamically using AddHandler
Dim ep1 As New EventPublisher
ep1.Number = 101
'Attach an event to the handler
AddHandler ep1.NumberChanged, AddressOf TestIt
ep1.Number = 102
End Sub
Shared Sub TestIt()
Console.WriteLine("Number is modified")
End Sub
End Class
编写handler方法很简单-只需编写一个Sub
,它不接受任何参数并显示一个消息框
然后,您需要为事件订阅处理程序,您可以在方法中添加子句:
Sub ShowMessageBox() Handles foo.TestEvent
或者通过使用语句:
AddHandler foo.TestEvent, AddressOf ShowMessageBox
请注意,要遵循.NET约定,您的委托应该有两个参数—一个是类型Object
,用于指定引发事件的对象;另一个是类型EventArgs
或子类,用于提供任何额外信息。这不是语言所要求的,但它是一种广泛遵循的约定。编写处理程序方法很简单-只需编写一个不带参数并显示消息框的Sub
然后,您需要为事件订阅处理程序,您可以在方法中添加子句:
Sub ShowMessageBox() Handles foo.TestEvent
或者通过使用语句:
AddHandler foo.TestEvent, AddressOf ShowMessageBox
请注意,要遵循.NET约定,您的委托应该有两个参数—一个是类型Object
,用于指定引发事件的对象;另一个是类型EventArgs
或子类,用于提供任何额外信息。这不是语言所要求的,但它是一个广泛遵循的惯例。为什么这些说明中不包括附件部分:?在某些情况下是否存在隐含的附件?@PaulLassiter:该页面是关于引发一个事件的,可以说是“服务器”端。附加事件处理程序是“客户端”端。仅供参考,更新后的文件确实涵盖了Paul在“事件处理程序”部分的代码示例中提到的内容:AddHandler c.ThresholdReach,AddressOf c_ThresholdReach
,用于VB。为什么这些说明中不包括附件部分:?在某些情况下是否存在隐含的附件?@PaulLassiter:该页面是关于引发一个事件的,可以说是“服务器”端。附加事件处理程序是“客户端”端。仅供参考,更新后的文件确实涵盖了Paul在“事件处理程序”部分的代码示例中提到的内容:AddHandler c.ThresholdReach,AddressOf c_ThresholdReach
,用于VB。为什么这些说明中不包括附件部分:?在某些情况下是否存在隐含附件?为什么这些说明中不包括附件部分:?在某些情况下是否存在隐性依恋?