public ActionResult Sub(string ma, int soluong) { ShoppingCart Cart = (ShoppingCart)Session["cart"]; if (Cart == null) { Cart = new ShoppingCart(); } ProductsDao dao = new ProductsDao(); Product pro = dao.FindProduct(ma); Cart.SubItem(pro, soluong); Session["cart"] = Cart; return(Redirect(Request.UrlReferrer.ToString())); }