Public Sub TreeView1_DoubleClick(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles TreeView1.DoubleClick
        Dim tn As TreeNode
        tn = TreeView1.GetNodeAt(TreeView.PointToClient( _
        TreeView1.MousePosition()))
        If Not IsNothing(tn) Then
            TreeView1.SelectedNode = tn
            '....Reaktion auf Doppelklick
        End If
 
    End Sub