private void btnShowKHQL_Click(object sender, EventArgs e)
        {
            FormAddKhachHang f = new FormAddKhachHang();

            f.Show();
        }
        private void btnThanhToan_chonKH_Click(object sender, EventArgs e)
        {
            FormAddKhachHang f = new FormAddKhachHang();

            f.Show();
        }