VB.NET調用可以到窗口句柄已創建不能在一個控件調用，但手柄創建

Question

這是我的情況，有2個班，我的主窗體Form1：

Class1的：有一個方法doSomethingAndCall（回調），它創建了一個新的線程 類2：具有動態創建的控件有一個按鈕，觸發Class1.doSomethingAndCall（newCallback）

代碼它看起來像這樣（它開始於Class2.Button_Click）：

Class Class1 
    public shared sub doSomethingAndCallAsync(state as object) 
    Console.WriteLine(Form1.InvokeRequired) 'output: false 
    Console.WriteLine(Form1.IsHandleCreated) 'output: false 
    Form1.Invoke(state.callback) 'throws System.InvalidOperationException 
    end sub 

    public shared sub doSomethingAndCall(callback as object) 
    System.Threading.ThreadPool.QueueUserWorkItem(AddressOf doSomethingAndCallAsync, New With {.callback = callback}) 
    end sub 
End Class 

Class Class2 
    Public Delegate Sub doSomethingDelegate() 

    Public Sub doSomething() 
    Console.WriteLine("success!") 
    End Sub 

    Public Sub Button_Click(ByVal sender As Object, ByVal e As System.EventArgs) 
    Class1.doSomethingAndCall(New doSomethingDelegate(AddressOf doSomething)) 
    End Sub 
End Class 

ex行爲例外，我得到的是：

調用或BeginInvoke可直到窗口句柄已創建

不能在控制打來電話，我可以看到Console.WriteLine命令行中4顯示我，形式是真的沒有創建。所以我說這個處理程序，現在它得到的真正困惑：

Private Sub Form1_HandleCreated(sender As Object, e As System.EventArgs) Handles Me.HandleCreated 
     Console.WriteLine("Handle created") 'Output: Handle created, when running program 
    End Sub 

    Private Sub Form1_HandleDestroyed(sender As Object, e As System.EventArgs) Handles Me.HandleDestroyed 
     Console.WriteLine("Handle destroyed") 'Will never Output! 
    End Sub 

所以它的創建和銷燬從來沒有，但如果我按一下按鈕它仍然不是avaible？ - 任何人都可以解釋我發生了什麼以及如何調用回調正確，謝謝！

Answer 1

My.Forms.Form1 aka的實例。 Form1將在每個線程中有所不同。您需要處理正確的實例。拖放一個按鈕到您的Form1，並添加以下代碼：

Public Class Form1 

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click 
     Threading.Tasks.Task.Factory.StartNew(Sub() Class1.Wrong()) 
     Threading.Tasks.Task.Factory.StartNew(Sub() Class1.Correct(Me)) 
    End Sub 

End Class 

Public Class Class1 

    Public Shared Sub Wrong() 
     Debug.WriteLine(String.Format("(Other thread, wrong) InvokeRequired={0}, IsHandleCreated={1}", Form1.InvokeRequired, Form1.IsHandleCreated)) 
    End Sub 

    Public Shared Sub Correct(instance As Form1) 
     Debug.WriteLine(String.Format("(Other thread, correct) InvokeRequired={0}, IsHandleCreated={1}", instance.InvokeRequired, instance.IsHandleCreated)) 
    End Sub 

End Class 

輸出

（其它線程，正確的）InvokeRequired =真，IsHandleCreated =真

（其他線程，錯誤）InvokeRequired = False，IsHandleCreated = False