c# - ipad 上的会话为空

Question

我有以下代码在起作用：

public JsonResult AddTicketToCart(...)
{
   ... 
   Session.Add("Cart", cart);
   return Json(new { IsSuccess = true }, JsonRequestBehavior.AllowGet);
}

在 JS 代码中：

$.get('/desk/AddTicketToCart', { clientId: clientId, sessionId: sessionId, levelId: levelId, places: places, isWithoutPlace: isWithoutPlace, delivery: delivery }, function (data) {
     if (data.IsSuccess) {
          if (isQuickBuy)
              window.location = '/desk/paywizard';
          else
              window.location = $('#wiz_header .first-child>a').attr('href');
      } else {
                 toastr.options.timeOut = 10000;
                 toastr.error('Error.');
                }
            });

该PayWizard动作包含：

if (Session["Cart"] == null)
return new HttpNotFoundResult();

var model = CreateViewData<PersonalInfoViewData>();
return View("PersonalInformation", model);

问题在于我在 Ipad 上收到 404 错误。在桌面上一切正常。我将日志消息添加到AddTicketToCart：

public JsonResult AddTicketToCart(...)
    {
       ... 
       Session.Add("Cart", cart);

       if(Session["Cart"] != null)
            Logging.Log.Info("Cart not null");
       else
            Logging.Log.Info("Cart equal null");

        var test = (CartModel) Session["Cart"];
        if( test != null)
        {
            Logging.Log.Info("CartModel not null");
            Logging.Log.Info("Tickets count: {0}", test.Tickets.Count);
        }
        else
            Logging.Log.Info("CartModel equal null");

       return Json(new { IsSuccess = true }, JsonRequestBehavior.AllowGet);
    }

输出如下：

2012-11-02 09:37:34.4887 | Info | Cart not null 

2012-11-02 09:37:34.4887 | Info | CartModel not null 

2012-11-02 09:37:34.4887 | Info | Tickets count: 1 

如您所见Cart，会话中存在。ButinPaywizard等于 null。哪里有问题？