public ActionResult Add(int ID) { GioHang giohang = GetCart(); ThuCung x = db.ThuCungs.Find(ID); if (x == null) { return(View("Error")); } SanPham p = new SanPham(x.MaThuCung, x.TenThuCung, x.HinhAnh, (long)x.Gia, 1); giohang.AddToCart(p); return(RedirectToAction("Index")); }