private void buttonX2_Click(object sender, EventArgs e)
 {
     DonVi dv = new DonVi();
     dv.ShowDialog();
 }
 private void btMaDonVi_Click(object sender, EventArgs e)
 {
     DonVi dv = new DonVi();
     dv.ShowDialog();
     donViCtrl.HienThiComboBox(cmbMaDonVi);
 }