Protected Overrides Sub OnMouseDown(ByVal e As _
      System.Windows.Forms.MouseEventArgs)
        Try
            If e.Button = MouseButtons.Right Then
                ' wurde ein knoten angeklickt
                Dim aktNode As System.Windows.Forms.TreeNode
                aktNode = Me.GetNodeAt(e.X, e.Y)
                If aktNode Is Nothing Then
                    Return
                Else
                    Me.SelectedNode = aktNode
                End If
            End If