private void bn_insert_ItemClick(object sender, ItemClickEventArgs e)
        {
            frm_MatHang_ThemMatHang frm = new frm_MatHang_ThemMatHang();

            frm.ShowDialog();
            refress();
        }
        private void barButtonItem1_ItemClick(object sender, ItemClickEventArgs e)
        {
            frm_MatHang_ThemMatHang frm = new frm_MatHang_ThemMatHang();

            frm.ShowDialog();
        }