public IActionResult Them(int id)
        {
            var x = _iSanPham.LayTatCaSanPham().FirstOrDefault(p => p.ID_SanPham == id);

            if (x != null)
            {
                _gioHang.ThemSanPhamVaoGioHang(x, 1);
            }
            return(RedirectToAction("giohang"));
        }