Private Sub CutToolStripMenuItem_Click(ByVal sender As System.Object, ByVal _
      e As System.EventArgs) Handles CutToolStripMenuItem.Click
        If ContextMenuStrip1.SourceControl IsNot Nothing Then
            CType(ContextMenuStrip1.SourceControl, TextBox).Cut()
        Else
            CType(Me.ActiveControl, TextBox).Cut()
        End If
    End Sub

   Private Function GetControl(ByVal cm As ContextMenuStrip, ByVal ct As Type) _
     As Control
        Dim ctl As Control = cm.SourceControl
        If cm.SourceControl Is Nothing Then
            ctl = Me.ActiveControl
        End If
        If ctl Is Nothing Then Return Nothing
        If ctl.GetType Is ct Then Return ctl
        Return Nothing
    End Function
 
    Private Sub PasteToolStripMenuItem_Click(ByVal sender As System.Object, _
      ByVal e As System.EventArgs) Handles PasteToolStripMenuItem.Click
        Dim tb As TextBox = CType(GetControl(ContextMenuStrip1, GetType( _
        TextBox)), TextBox)
        If tb IsNot Nothing Then tb.paste()
    End Sub

    Private Function GetControl(Of T As Control)(ByVal cm As ContextMenuStrip) _
      As T
        Dim ctl As Control = cm.SourceControl
        If cm.SourceControl Is Nothing Then
            ctl = Me.ActiveControl
        End If
        If ctl Is Nothing Then Return Nothing
        If TypeOf ctl Is T Then Return CType(ctl, T)
        Return Nothing
    End Function
 
    Private Sub PasteToolStripMenuItem_Click(ByVal sender As System.Object, _
      ByVal e As System.EventArgs) Handles PasteToolStripMenuItem.Click
        Dim tb As TextBox = GetControl(Of TextBox)(ContextMenuStrip1)
        If tb IsNot Nothing Then tb.paste()
    End Sub

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Alle Angaben ohne Gewähr. Keine Haftung für Vorschläge, Tipps oder sonstige Hilfe, falls es schiefgeht, nur Zeit verschwendet oder man sonst nicht zufrieden ist