''' <summary>Suche nach dem Knoten mit einem bestimmten Text</summary>
''' <param name="tnc">zu durchsuchende Knoten-Auflistung</param>
''' <param name="Text">zu suchender Text (Groß-/Kleinschreibung ignoriert)</param>
''' <param name="Level">der zu durchsuchende Knotenlevel (-1: alle Ebenen)</param>
''' <returns>der gesuchte Knoten (oder Nothing)</returns>
Private Function FindNode(tnc As TreeNodeCollection, ByVal Text As String, _
                   Optional ByVal Level As Integer = -1) As TreeNode
 
    If String.IsNullOrEmpty(Text) Then Return Nothing
 
    Dim TextToFind As String = Text.Trim.ToLower
    Dim tnFound As TreeNode
 
    For Each tnCurr As TreeNode In tnc
       If tnCurr.Text.Trim.ToLower = TextToFind Then
          If Level < 0 Then
             Return tnCurr
          ElseIf Level = tnCurr.Level Then
             Return tnCurr
          End If
       End If
 
       tnFound = FindNode(tnCurr.Nodes, Text, Level)
       If tnFound IsNot Nothing Then Return tnFound         
   Next tnCurr
 
   Return Nothing
End Function

   Dim tf As TreeNode = FindNode(trv.Nodes, " tralala ", 1)
   If tf IsNot Nothing Then
      tf.Expand()
      trv.SelectedNode = tf
   End If