Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button2.Click
' meine Variante den Baum zu füllen 
        Dim geraetenameN, teilenameN, endteilN As GeraeteTreeNode
        For Each geraetename As DataRow In dtA1.Rows
            geraetenameN = New GeraeteTreeNode(geraetename.Item(1).ToString, _
              New Geraete(0, 99, "Test1"))
            For Each teilename As DataRow In dtA2.Rows
                If geraetename.Item(0).Equals(teilename.Item(1)) Then
                    teilenameN = New GeraeteTreeNode(teilename.Item( _
                      2).ToString, New Geraete(1, 199, "Test2"))
                    For Each endteil As DataRow In dtA3.Rows
                        If teilename.Item(0).Equals(endteil.Item(1)) Then
                            endteilN = New GeraeteTreeNode(endteil.Item(2), New _
                              Geraete(1, 299, "Test3"))
                        End If
                    Next
                End If
            Next
            Me.TreeView1.Nodes.Add(geraetenameN)
        Next
    End Sub
    Private Sub TreeView1_AfterSelect(ByVal sender As System.Object, ByVal e As _
      System.Windows.Forms.TreeViewEventArgs) Handles TreeView1.AfterSelect
' hier kannst  du jetzt alle Informationnen des angeklicken Node in Erfahrung 
' bringen
        MessageBox.Show(CType(e.Node, _
          GeraeteTreeNode).GeraeteInformationen.Ebene.ToString)
        MessageBox.Show(CType(e.Node, _
        GeraeteTreeNode).GeraeteInformationen.GeraeteName.ToString)
        MessageBox.Show(CType(e.Node, _
        GeraeteTreeNode).GeraeteInformationen.GeraeteNummer.ToString)
    End Sub
'die "neuen" Klassen die uns das Leben etwas einfacher machen sollen:
Public Class Geraete
    Public Sub New(ByVal Ebene As Int32, ByVal GeraeteNummer As Int32, ByVal _
      GeraeteName As String)
        Me.Ebene = Ebene
        Me.GeraeteNummer = GeraeteNummer
        Me.GeraeteName = GeraeteName
    End Sub
    Public Ebene As Integer 'Ersatz für Tag
    Public GeraeteNummer As Integer
    Public GeraeteName As String
End Class
Public Class GeraeteTreeNode : Inherits TreeNode
    Public GeraeteInformationen As Geraete
    Public Sub New(ByVal Text As String, ByVal GeraeteInformationen As Geraete)
        MyBase.New()
        MyBase.Text = Text
        Me.GeraeteInformationen = GeraeteInformationen
    End Sub
End Class