private void libBookingID_SelectedIndexChanged(object sender, EventArgs e) { libDemoNumber.Items.Clear(); List <string> demonumbers = new List <string>(); int bookingIdSelected = Convert.ToInt32(libBookingID.SelectedItem.ToString()); demonumbers = CC.GetDemoNumbersByBooking(bookingIdSelected); foreach (string s in demonumbers) { libDemoNumber.Items.Add(s); } }