protected void AddToCartButton_Click(object sender, EventArgs e)
        {
            using (ToyStoreEntities context = new ToyStoreEntities())
            {
                String CurrentUserName = ((Site1)Page.Master).CurrentUserName;
                Cart myCart;
                //找到该用户的购物车
                var query = from p in context.Carts
                            where p.UserName == CurrentUserName
                            select p;
                if (query.Count() == 0)
                {
                    myCart = new Cart();
                    myCart.UserName = CurrentUserName;
                    context.AddToCarts(myCart);
                }
                else
                {
                    myCart = query.First();
                }
                //查找是否已有该购物车明细
                var query1 = from p in myCart.CartDetails
                             where p.Product.Id == CurrentProduct.Id
                             select p;
                CartDetail myCartDetail;
                if (query1.Count() == 0)
                {
                    //如果没有,新增
                    myCartDetail = new CartDetail();
                    myCartDetail.Cart = myCart;
                    myCartDetail.ProductId = CurrentProduct.Id;
                    myCartDetail.OTY = 1;

                }
                else
                {
                    //如果有,修改数量
                    myCartDetail = query1.First();
                    myCartDetail.OTY += 1;
                }
                context.SaveChanges();
            }
        }