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我刚刚学会了如何在单独的线程中设置 GUI...

Private myGui As SomeGui
Public Class myAsyncState
    Public a As Boolean = True
    Public b As Integer = 100
End Class

Public Sub Caller()
    '
    myGui = New SomeGui()
    ' setup
    myGui.Begin()
    Dim a as Boolean = False
    Dim b as Integer = 1
    Dim state As myAsyncState = New myAsyncState(a, b)
    Dim step1 As New xDelegate(AddressOf xMethod)
    Dim callBack As New AsyncCallback(AddressOf xMethod_Callback)            
    Dim asyncResultTest As IAsyncResult = step1.BeginInvoke(a, b, callBack, state)

End Sub

Private Delegate Sub xDelegate(Byval a as Integer, ByVal b As Boolean) 
Public Sub xMethod(Byval a as Integer, ByVal b As Boolean)     
End Sub

Private Sub xMethod_Callback(ByVal ia As IAsyncResult)
    Dim myAsyncResult As AsyncResult = CType(ia, AsyncResult)
    Dim myAsyncMethodCaller As xDelegate = CType(myAsyncResult.AsyncDelegate, xDelegate)
    Dim state As myAsyncState = CType(myAsyncResult.AsyncState, myAsyncState)
    myAsyncMethodCaller.EndInvoke(ia)
    xMethod_Finish(state.a, state.b)
End Sub

Private Sub xMethod_Finish(ByVal a As Integer, ByVal b As Boolean)
    If Me.InvokeRequired Then
      Invoke(New xDelegate(AddressOf xMethod_Finish), New Object() {a, b})   ' here

' Also tried Invoke(New xDelegate(AddressOf xMethod_Finish), a, b)   though the above is what I have seen in documentation
' also tried to make Dim state As myAsyncState = New myAsyncState(a, b) and use it as an argument
        Else
            yMethod(a, b)
            myGui.Finish()
        End If
    End Sub

我正在返回和传递值，一切都很好......然后我返回它进行测试，并得到一个错误：

A first chance exception of type 'System.Collections.Generic.KeyNotFoundException' occurred in mscorlib.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in mscorlib.dll

An unhandled exception of type 'System.Collections.Generic.KeyNotFoundException' occurred in System.Windows.Forms.dll

Additional information: The given key was not present in the dictionary.

例外是在“xMethod”完成后，在我显示“here”的那一行 - 在 xMethod_Finish 中。看起来有一些不匹配的参数 - 但我认为它们都是正确的 - 我付出了很多努力来理解如何将参数传递给委托，以便它们也可以在 EndInvoke 之后传递给后续方法第一个（仍将在 GUI 线程中）。

请帮我看看我做错了什么。谢谢你。

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1 回答 1

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您的调用看起来正确。

错误可能在yMethodormyGui.Finish()方法中。当异常发生在被调用的方法中时，它们可能会变得有点隐藏。检查异常的InnerException属性以获取更多信息以及导致KeyNotFoundException.

您可以在问题方法中设置断点来调试错误。

于 2013-01-29T00:08:44.180 回答