Sub test()
        Dim i As Integer
        Dim tn As TreeNode
        Dim tn_ As TreeNode
        TreeView1.Nodes.Clear()
        TreeView1.BeginUpdate()
        For i = 0 To 15
            tn = New TreeNode("Knoten " & i)
            TreeView1.Nodes.Add(tn)
            If i = 10 Then tn_ = tn
        Next i
        TreeView1.EndUpdate()
        Dim tncoll As TreeNodeCollection = TreeView1.Nodes
        If tncoll.Contains(tn_) Then MessageBox.Show("Knoten schon vorhanden ")
    End Sub