Imports System.Data.OleDb
 
Public Class Form5
    Private conn As OleDbConnection = Nothing
    Private daLA As OleDbDataAdapter = Nothing
    Private daBL As OleDbDataAdapter = Nothing
    Private daSt As OleDbDataAdapter = Nothing
    Private ds As DataSet = Nothing
 
    Private Sub Form5_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
 
        Dim DatenBank As String
        Dim bs As New BindingSource
        Dim bsLandBL As New BindingSource
        Dim bsBLStadt As New BindingSource
        DatenBank = Application.StartupPath & "\Daten.mdb"
        conn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data" & _
          "Source=" & DatenBank)
 
        ds = New DataSet
        daLA = New OleDbDataAdapter("Select * from Land", conn)
        daBL = New OleDbDataAdapter("Select * from Bundesland", conn)
        daSt = New OleDbDataAdapter("Select * from Hauptstadt", conn)
        daLA.FillSchema(ds, SchemaType.Mapped, "Land")
        daBL.FillSchema(ds, SchemaType.Mapped, "Bundesland")
        daSt.FillSchema(ds, SchemaType.Mapped, "Hauptstadt")
 
        ds.Relations.Add("LandBL", ds.Tables("Land").Columns("LandID"), _
        ds.Tables("Bundesland").Columns("LandID"))
 
        ds.Relations.Add("BLStadt", ds.Tables("Bundesland").Columns("BLID"), _
        ds.Tables("Hauptstadt").Columns("StID"))
        daLA.Fill(ds, "Land")
 
        daBL.Fill(ds, "Bundesland")
        daSt.Fill(ds, "Hauptstadt")
 
        bs.DataSource = ds
        bs.DataMember = "Land"
        bsLandBL.DataMember = "LandBL"
        bsLandBL.DataSource = bs
        bsBLStadt.DataMember = "BLStadt"
        bsBLStadt.DataSource = bsLandBL
 
        ComboBox1.DisplayMember = "Land"
        ComboBox2.DisplayMember = "BL"
        ComboBox3.DisplayMember = "Stadt"
        ComboBox1.DataSource = bs
        ComboBox2.DataSource = bsLandBL
        ComboBox3.DataSource = bsBLStadt
    End Sub
 
End Class