private void btnNewDH_Click(object sender, EventArgs e)
        {
            LapDonHang lapDonHang = new LapDonHang();

            lapDonHang.Show();
        }
        private void orderToolStripMenuItem_Click(object sender, EventArgs e)
        {
            LapDonHang lapDonHang = new LapDonHang();

            addForm(lapDonHang);
        }