Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Try
            Dim baglanti As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source='turkiye.mdb'") 'Veritabanımızın yerini belirtiyoruz.

            Dim sorgu As New OleDbCommand("SELECT * FROM il ORDER BY il_id", baglanti)
            Dim oku As OleDbDataReader = Nothing
            baglanti.Open()
            oku = sorgu.ExecuteReader()
            ComboBox1.Items.Clear()
            While oku.Read()
                ComboBox1.Items.Add(oku("il_ad").ToString())
            End While
            oku.Close()
            baglanti.Close()
        Catch
            MessageBox.Show("iller listelenemedi.")
        End Try
    End Sub

Private Sub ComboBox2_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox2.SelectedIndexChanged

        Try
            Dim baglanti As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source='turkiye.mdb'") 'Veritabanımızın yerini belirtiyoruz.

            ComboBox2.Items.Clear()
            Dim komuturundoldur As New OleDbCommand("SELECT * FROM ilce WHERE il_id like'" & (ComboBox2.SelectedIndex + 1) & "'", baglanti)
            Dim oku As OleDbDataReader = Nothing
            baglanti.Open()
            oku = komuturundoldur.ExecuteReader()
            While oku.Read()
                ComboBox2.Items.Add(oku("ilce_ad").ToString())
            End While
            oku.Close()
            baglanti.Close()
        Catch
            MessageBox.Show("Ylçeler Syralamady", "Hata", MessageBoxButtons.OK, MessageBoxIcon.Warning)
        End Try




    End Sub

inceleyemiyorum ama bende şu şekilde 

Private Sub ilDoldur()
        Dim baglanti As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source='access.mdb'")
        Dim veriler As New DataTable("il")
        Dim adapter As New OleDbDataAdapter("select * from tblil order by il", baglanti)
        adapter.Fill(veriler)
        cbIl.ValueMember = "id"
        cbIl.DisplayMember = "il"
        cbIl.DataSource = veriler
    End Sub
    

  Private Sub ilceDoldur()
        Dim baglanti As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source='access.mdb'")
        Dim veriler As New DataTable("ilce")
        Dim adapter As New OleDbDataAdapter(String.Format("select * from tblilce where il_ID={0}", cbIl.SelectedValue.ToString), baglanti)
        adapter.Fill(veriler)
        cbIlce.DataSource = veriler
        cbIlce.DisplayMember = "ilce"
    End Sub
  

 Dim baglanti As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source='KENDİDOSYAADINI.mdb'")
        Dim veriler As New DataTable("il")
        Dim adapter As New OleDbDataAdapter("select * from KEDNİTABLOADINI order by KENDİİLALANADINI", baglanti)

Private Sub doktorkayit_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
 ilDoldur()
 End Sub

Private Sub ilDoldur()
 Dim baglanti As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source='access.mdb'")
 Dim veriler As New DataTable("il")
 Dim adapter As New OleDbDataAdapter("select * from tblil order by il", baglanti)
 adapter.Fill(veriler)
 cbIl.ValueMember = "id"
 cbIl.DisplayMember = "il"
 cbIl.DataSource = veriler
 End Sub
 

 Private Sub cbIl_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cbIl.SelectedIndexChanged
 ilceDoldur()
 End Sub

 Private Sub ilceDoldur()
 Dim baglanti As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source='access.mdb'")
 Dim veriler As New DataTable("ilce")
 Dim adapter As New OleDbDataAdapter(String.Format("select * from tblilce where il_ID={0}", cbIl.SelectedValue.ToString), baglanti)
 adapter.Fill(veriler)
 cbIlce.DataSource = veriler
 cbIlce.DisplayMember = "ilce"
 End Sub