vb.net声明事件的两种方式

Handles 关键字和 AddHandler 语句都允许您指定特定过程处理特定事件，但存在差异。定义过程时请使用 Handles 关键字以指定该过程处理特定事件。AddHandler 语句在运行时将过程连接到事件。（摘自MSDN）

（1）

Public Class ContainerClass ' Module or class level decl<a href="https://www.jb51.cc/tag/ara/" target="_blank" class="keywords">ara</a>tion. WithEvents Obj As New Class1 '和Handles关联 Public Class Class1 ' Declare an event. Public Event Ev_Event() Sub CauseSomeEvent() ' Raise an event. RaiseEvent Ev_Event() End Sub End Class Sub EventHandler() Handles Obj.Ev_Event ' Handle the event. Msg<a href="https://www.jb51.cc/tag/Box/" target="_blank" class="keywords">Box</a>("EventHandler caught event.") End Sub ' Call the TestEvents procedure from an instance of the ContainerClass ' class to test the Ev_Event event and the event handler. Public Sub TestEvents() Obj.CauseSomeEvent() End Sub End Class

（2）

Sub TestEvents() Dim Obj As New Class1 ' Associate an event handler with an event. AddHandler Obj.Ev_Event,AddressOf EventHandler ' Call the method to raise the event. Obj.CauseSomeEvent() ' Stop handling events. RemoveHandler Obj.Ev_Event,AddressOf EventHandler ' This event will not be handled. Obj.CauseSomeEvent() End Sub Sub EventHandler() ' Handle the event. Msg<a href="https://www.jb51.cc/tag/Box/" target="_blank" class="keywords">Box</a>("EventHandler caught event.") End Sub Public Class Class1 ' Declare an event. Public Event Ev_Event() Sub CauseSomeEvent() ' Raise an event. RaiseEvent Ev_Event() End Sub End Class

实例：

CustomerEventArgs.vb: Public Class CustomerEventArgs Inherits Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank" class="keywords">stem</a>.EventArgs Private m_name As String Private m_age As Integer Public Sub New() End Sub Public Sub New(ByVal _name As String,ByVal _age As Integer) Me.Name = _name Me.Age = _age End Sub Public Property Name() As String Get Return m_name End Get Set(ByVal value As String) m_name = value End Set End Property Public Property Age() As Integer Get Return m_age End Get Set(ByVal value As Integer) m_age = value End Set End Property End Class Employee.vb Public Class Employee Public Event PlayGame(ByVal sender As Object,ByVal e As CustomerEventArgs) Dim cea As New CustomerEventArgs("zhang",20) Public Sub Game() RaiseEvent PlayGame(Me,cea) End Sub End Class Admin.vb: Public Class Admin 'Notify()和事件Employee.PlayGame的签名相同 Public Sub Notify(ByVal sender As Object,ByVal e As CustomerEventArgs) Message<a href="https://www.jb51.cc/tag/Box/" target="_blank" class="keywords">Box</a>.Show(e.Name & ":" & e.Age.ToString() & "is playing game!") End Sub End Class FormEvent.vb '此窗体上有两个按钮Button1（<a href="https://www.jb51.cc/tag/tianjia/" target="_blank" class="keywords">添加</a>事件），Button2（取消事件） Public Class FormEvent '注释部分为<a href="https://www.jb51.cc/tag/tianjia/" target="_blank" class="keywords">添加</a>事件的第二种<a href="https://www.jb51.cc/tag/fangfa/" target="_blank" class="keywords">方法</a> Dim emp As New Employee() 'Dim WithEvents eventEmp As New Employee() ‘由Handles处理 Dim ad As New Admin() Private Sub Button1_Click(ByVal sender As Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank" class="keywords">stem</a>.Object,ByVal e As Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank" class="keywords">stem</a>.EventArgs) Handles Button1.Click 'eventEmp.Game() AddHandler emp.PlayGame,AddressOf ad.Notify emp.Game() End Sub '该过程的签名必须与 eventlist 中各事件的签名相匹配 'Private Sub emp_PlayGame(ByVal sender As Object,ByVal e As CustomerEventArgs) Handles eventEmp.PlayGame ' ad.Notify(sender,e) 'End Sub Private Sub Button2_Click(ByVal sender As Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank" class="keywords">stem</a>.Object,ByVal e As Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank" class="keywords">stem</a>.EventArgs) Handles Button2.Click RemoveHandler emp.PlayGame,AddressOf ad.Notify End Sub End Class

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