Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim conString As String
        conString = "Server=bla;database=bla;User ID=bla;Pwd=bla"
        Dim con As SqlConnection = Nothing
        Dim row As DataRow
        Dim da As SqlDataAdapter
        Dim dt As New DataTable
 
        Try
            con = New SqlConnection(conString)
            con.Open()
            MessageBox.Show("Offen")
 
            da = New SqlDataAdapter("SELECT Kategorie FROM dbo.Test ", con)
            da.Fill(dt)
            DataGridView1.DataSource = dt
 
 
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        Finally
 
        End Try
 
End Sub
End Class

        Try
            con = New SqlConnection(conString)
            con.Open()
            MessageBox.Show("Offen")
 
            da = New SqlDataAdapter("SELECT Kategorie,Unterkategorie, Fehler," & _
              "Ursache FROM dbo.Hallo ", con)
            da.Fill(dtb)
            DataGridView1.DataSource = dtb
 
            da.SelectCommand.CommandText = "SELECT Kategorie " & _
                                        "FROM dbo.Hallo"
            da.SelectCommand.CommandType = CommandType.Text
 
            dt = New DataTable("")
            ds.Tables.Add(dt)
 
            da.Fill(dt)
 
 
            Dim Zeile As DataRow
            For I = 0 To dt.Rows.Count - 1
                Zeile = dt.Rows(I)
                ComboBox1.Items.Add(Zeile.Item(0))
            Next
 
 
 
 
 
        Catch ex As Exception
            MessageBox.Show(ex.Message)
 
        End Try

'Die beiden Comboboxen
Dim WithEvents cboKat As New ComboBox With {.Parent = Me, .Left = 400}
Dim cboUnterKat As New ComboBox With {.Parent = Me, .Left = 400, .Top = 50}
 
'Tabelle mit Daten aus der Datenbank
Dim dt As New DataTable
Dim bs As New BindingSource
 
 
'Im Load-Event der Form
 
'Kategorien ermitteln (als Liste)
Dim klst As List(Of String) = _
           (From row As Object In dt.Rows _
            Select DirectCast(row, DataRow).Field(Of String)("Kategorie") _
            Distinct).ToList
 
cboKat.DataSource = klst
 
'Unterkategorie-Spalte an Combo binden
bs.DataSource = dt
cboUnterKat.DisplayMember = "Unterkategorie"
cboUnterKat.DataSource = bs
 
 
'Und dann ....
Private Sub cboKat_SelectedValueChanged(sender As Object, _
        e As System.EventArgs) Handles cboKat.SelectedValueChanged
 
    If bs.Count = 0 Then Exit Sub
 
    Dim filterstring As String = "Kategorie = '" & cboKat.Text & "'"
    bs.Filter = filterstring 'Filtersting gemäß Kategorienauswahl setzen
End Sub