private void cbxLoaiPhong_SelectedIndexChanged(object sender, EventArgs e) { string loaiPhong = cbxLoaiPhong.GetItemText(cbxLoaiPhong.SelectedItem); RoomAccess data = new RoomAccess(); DataTable dt = new DataTable(); dt = data.loadIDCost(loaiPhong); cbxMaPhong.DisplayMember = "roomno"; cbxMaPhong.DataSource = dt; cbxtienPhong.DisplayMember = "price"; cbxtienPhong.DataSource = dt; txtCostPerDay.Text = cbxtienPhong.GetItemText(cbxtienPhong.SelectedItem); cost = float.Parse(txtCostPerDay.Text); caculteMoney(); }