如何使用VB.Net从表单事件中删除所有处理程序？ [英] how to remove all handler from an event of form using VB.Net?

问题描述

我正在开发一个窗口应用程序（使用Vb编写。在主窗体Load事件中，还加载了另一种形式'frmcrew_managment'。在此阶段，对于主窗体的RefreshClick事件，
附加'frmcrew_managment'的'Refreshadata'方法（处理程序）。因此，在加载主窗体后，它的RefreshClick事件具有'frmcrew_managment'方法的地址。现在在主窗体中，菜单选项之一是OpenAdjustment（frmOpenAdjustment
）。所以onclick的OpenAdjustment选项，在它的表单加载（对于frmOpenAdjustment）我需要将RefreshGriddata方法（frmOpenAdjustment）附加到Main Form的RefreshClick事件，当用户点击主屏幕上的Refresh时，刷新frGOpenAdjustment
的方法被调用。但是现在发生的事情正在发生的frmcrew_managment的Refreshadata也被调用了。因此，为了解决这个问题，我需要在添加frmOpenAdjustment的事件处理程序RefreshGriddata之前从主Form的RefreshClick事件中删除所有事件处理程序。那么
是从主窗体的事件（RefreshClick）中删除所有事件处理程序的方法吗？



我尝试了什么：



Private _parent As frmMainAlt

Private _Me as frmOpenAdjustmentsAlt

Private _crewMgt As frmCrewManagement



_ parent = parent





RemoveHandler _parent.RefreshClick，AddressOf _crewMgt.RefreshData



AddHandler _parent.RefreshClick，AddressOf refreshgrid

这里的要求是默认情况下在所有情况下主要
表单的Refreshclick应该由frmcrew_managment的Refreshadata处理，但是当从菜单选项加载frmOpenAdjustment时，主表单的Refreshclick应该由frmOpenAdjustment的RefreshGriddata处理  

推荐答案

基本的经验法则是跟踪处理程序，订阅，完成后，取消订阅。

The base rule of thumb is to keep track of handlers, subscribe, when done, unsubscribe.

我可能错了，但是这里有人（可能是里德）可能写过这个。

I may be wrong but someone here (possibly Reed) may have written this.

Public Class Form1

    Dim object1 As New Button

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        AddHandler object1.Click, AddressOf Object1_Click
    End Sub

    Private Sub Object1_Click(ByVal sender As Object, ByVal e As System.EventArgs)

    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        'NB: EventName is case sensitive
        If HandlerContains(object1, "Object1_Click", "Click") Then
            MsgBox("Found Handler")
        End If
    End Sub

    Private Function HandlerContains(ByVal Obj As Control, ByVal TheMethod As String, ByVal EventName As String) As Boolean
        Dim T = Obj.GetType.GetProperty("Events", Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Instance)
        Dim Key = GetType(Control).GetField("Event" & EventName, Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Static).GetValue(Obj)
        Dim EventHandlerList = T.GetValue(Obj, New Object() {})
        Dim MethodFind = EventHandlerList.GetType.GetMethod("Find", Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Instance)
        Dim ListEntry = MethodFind.Invoke(EventHandlerList, New Object() {Key})
        Dim Del = ListEntry.GetType.GetField("handler", Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Instance)
        Dim MultiCastDelegate = Del.GetValue(ListEntry)
        Dim MethodGIL = MultiCastDelegate.GetType.GetMethod("GetInvocationList")
        Dim EvocationList() As [Delegate] = CType(MethodGIL.Invoke(MultiCastDelegate, Nothing), [Delegate]())
        For Each Target As [Delegate] In EvocationList
            If Target.Method.Name = TheMethod Then
                Return True
            End If
        Next
        Return False
    End Function

End Class

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