Function lade_hauptnodes()
 
        Dim dt As DataTable = New DataTable("warengruppe")
        Dim Haupt_Tn As TreeNode
        Dim Tn As TreeNode
 
        Dim sCN As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & _
          projektdatenbank
        Dim sqlkommando As String= "Select * FROM stamm_warengruppen ORDER BY" & _
        "parent_id, bezeichnung"
 
        Dim cn As OleDb.OleDbConnection = New OleDb.OleDbConnection(sCN)
        Dim da As OleDb.OleDbDataAdapter = New OleDb.OleDbDataAdapter( _
          sqlkommando, cn)
        Dim cmd As OleDb.OleDbCommandBuilder = New OleDb.OleDbCommandBuilder(da)
        da.Fill(dt)
 
        With TreeView
 
            .SelectedNode = Nothing
            .Nodes.Clear()
 
            .BeginUpdate()
 
            Haupt_Tn = New TreeNode("Warengruppen")
            .Nodes.Add(Haupt_Tn)
 
            For Each r As DataRow In dt.Rows
 
                Tn = New TreeNode(r("bezeichnung"))
 
                If r("parent_id") = 0 Then
                    Haupt_Tn.Nodes.Add(Tn)
                    lade_subnodes(Tn, dt, r("warengruppe_id"))
                Else
                    Exit For
                End If
 
            Next
 
            .EndUpdate()
 
        End With
 
    End Function
 
    Private Function lade_subnodes(ByRef tn As TreeNode, ByRef dt As DataTable, _
      ByVal ID As Integer)
 
        Dim foundRows() As DataRow = dt.Select("parent_id = " + ID.ToString, _
          "bezeichnung")
        Dim Tn_Sub As TreeNode
 
        For Each _r As DataRow In foundRows
 
            Tn_Sub = New TreeNode(_r("bezeichnung"))
            tn.Nodes.Add(Tn_Sub)
            lade_subnodes(Tn_Sub, dt, _r("warengruppe_id"))
 
        Next
 
    End Function