public ActionResult ThemSanPham(ThemSanPhamGioHangVM vm)
        {
            rd = new Random();

            try
            {
                vuong_cms_context __db = new vuong_cms_context();
                var sanpham            = __db.Product.Find(vm.SanPhamId);

                CTGioHang ct = new CTGioHang();
                ct.SanPhamId  = vm.SanPhamId;
                ct.TenSanPham = sanpham.ProductName;
                ct.HinhAnh    = sanpham.ThumbnailImage;
                ct.SoLuong    = vm.SoLuong;
                ct.Link       = Url.Action("Detail", "SanPham", new { id = sanpham.Id, seo_title = sanpham.ProductName.URLFriendly() });
                GioHang.ThemSanPham(ct);
            }
            catch (Exception ex)
            {
                return(Content("Lỗi: " + ex.Message));
            }
            return(RedirectToAction("Index"));
        }