private void btDSLoaiDichVu_Click(object sender, EventArgs e)
 {
     LoaiDichVu ldv = new LoaiDichVu();
     ldv.ShowDialog();
 }
 private void btMaLoaiDichVu_Click(object sender, EventArgs e)
 {
     LoaiDichVu ldv = new LoaiDichVu();
     ldv.ShowDialog();
     ldvCtrl.HienThiComboBox(cmbMaLoaiDV);
 }