cookie实现购物车

 #region 页面加载
    protected void Page_Load(object sender, EventArgs e)
    {
        //保存从跳转到当前页面的上一个页面地址
        //ViewState["Referer"] = Request.Headers["Referer"];
        if (!Page.IsPostBack)
        {
            //Request.Cookies.Clear();
            
            //保存从跳转到当前页面的上一个页面地址
            ViewState["Referer"] = Request.Headers["Referer"];
            AddProductToShopingCartCookie();
            BindShoppingCartInfoToGridView();
            Page.DataBind();
        }


    }
    #endregion 

    #region 将商品添加到购物车Cookie中
    //将购买的商品添加到保存购物信息的Cookie中
    protected void AddProductToShopingCartCookie()

    {
        //保存URL传递过来的商品Id
        int bookId;
        //定义bool型变量，判断URL传递过来的商品的ID是否在购物车Cookie中存在
        bool flag = false;
        //创建Cookie保存购物信息
        HttpCookie myCart = null;
        //定义临时保存Cookie的商品Id的Key
        string tempId = null;
        //判断购物车Cookie是否存在
        //if(Request.Cookies["LuciaShoppingCart"] == null)
        if (!object.Equals(Request.Cookies["ShoppingCart"], null))
        {
            //如果购物车存在，获取Cookie对象
            myCart = Request.Cookies["ShoppingCart"];
        }
        else
        {
            //创建Cookie对象
            myCart = new HttpCookie("ShoppingCart");
        }
        //往购物车里保存商品
        //从URL里获取传递过来的商品ID
        if (Request.QueryString["bookId"] != null)
        { 
            bookId = Convert.ToInt32(Request.QueryString["bookid"]);
            for (int i = 0; i < myCart.Values.Count; i++)
            {
                //获取每个名/值对的名，名是商品的ID，值是数量
                tempId = Request.Cookies["ShoppingCart"].Values.AllKeys[i];