private void btnTim_Click(object sender, EventArgs e) { luachon = cbb1.SelectedIndex; string text = txt1.Text; if (text != "") { if (luachon == 0) { BangTimKiem.DataSource = bus1.TimKiemTheoMaKhach(text); } else if (luachon == 1) { BangTimKiem.DataSource = bus2.TimKiemTheoMa(text); } else if (luachon == 2) { BangTimKiem.DataSource = bus3.TimKiemTheoMa(text); } } else { MessageBox.Show("Vui long nhap ma can tim"); } }