private void LoaiDuAn_LinkClicked(object sender, DevExpress.XtraNavBar.NavBarLinkEventArgs e)
 {
     if (formLoaiDuAn == null || formLoaiDuAn.IsDisposed)
     {
         formLoaiDuAn           = new QL_LoaiDuAn();
         formLoaiDuAn.MdiParent = this;
         formLoaiDuAn.Show();
     }
     else
     {
         formLoaiDuAn.Activate();
     }
 }
 private void button_loaiduan_Click(object sender, EventArgs e)
 {
     if (formLoaiDuAn == null || formLoaiDuAn.IsDisposed)
     {
         formLoaiDuAn           = new QL_LoaiDuAn();
         formLoaiDuAn.MdiParent = this;
         formLoaiDuAn.Show();
     }
     else
     {
         formLoaiDuAn.Activate();
     }
 }