using two combo box in windows application

Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
      If ComboBox1.SelectedItem.ToString() = "AP" Then
          ComboBox2.Items.Add("Medak")
 ComboBox2.Items.Add("Hyd")
'or bind combobox from db  also bind combobox2 here like  
 Dim cmd As SqlCommand = New SqlCommand()
        cmd.Connection = con
        cmd.CommandText = "select dist from district  where state='"+combobox1.selecteditem.tostring()+"'"
        con.Open()
        dr = cmd.ExecuteReader()
        If (dr.HasRows = True) Then
            While (dr.Read())
               ComboBox2.Items.Add(dr("dist").ToString())

            End While
        End If
        dr.Close()
        con.Close()
      End If

  End Sub