asp.net 网站 ajax调用后台webmethod 调用不到

悬赏园豆：20 [待解决问题]

原本网站是好好的都能正常调用不知道为啥就不行了哪位大侠帮我看看？不胜感激

前台

  <input class="btn_frgwc btnAddToCart" id="btnAddToCart" name="" type="button" value="" onclick="checkIsCusLogin('btnAddToCart', 'wydl', 'SetShopingCartInfo')" />

js：

function checkIsCusLogin(btnId, containerClass, callBack) {
    var rV = 0;
    $.ajax({
        type: "Post",
        url: "/CommonForm.aspx/CusIsLogin",
        //方法传参的写法一定要对，str为形参的名字,str2为第二个形参的名字  
        //data: "{'tourCode':'" + $('#reviewTourCode').val() + "','orderStar':'" + $('#orderStarScore').val() + "','serviceStar':'" + $('#serviceStarScore').val() + "','reviewTitle':'" + $('#reviewTitle').val() + "','reviewContent':'" + $('#reviewContent').val() + "'}",
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function (data) {
            alert(data);
            rV = data.d;
            //返回的数据用data.d获取内容 
            if (data.d == 0) {
                //$("." + containerClass).css("top", $(document).scrollTop() + 50);
                //$("." + containerClass).toggle();
                $('.' + containerClass).css(
                    { 
                        position:'absolute', 
                        left: ($(window).width() - $('.className').outerWidth())/2, 
                        top: ($(window).height() - $('.className').outerHeight())/2 + $(document).scrollTop()
                    }
                );
                $("." + containerClass).show();
            }
            else {
                $("." + containerClass).hide();
                if (callBack) {
                    eval(callBack + "('" + data.d + "')");
                }
            }
        },
        error: function (xhr, ajaxOptions, thrownError) {
            alert(xhr.status);
            alert(thrownError);
            alert(xhr.responseText);
        }
    });
    return rV;
}
后台webmethod：

 [WebMethod]
        public static string CusIsLogin()
        {
            object loginUser = HttpContext.Current.Session["loginUser"];
            if (loginUser == null)
            {
                return "0";
            }
            else
            {
                Object userName = HttpContext.Current.Session["loginUserName"];
                BLL.customers bllCus = new BLL.customers();
                Model.customers modCus = bllCus.GetModel(int.Parse(CommonUtil.MD5Decrypt(loginUser.ToString())));

                if (userName != null)
                {
                    return loginUser.ToString() + "|" + userName.ToString() + "|" + modCus.userEmail + "|" + modCus.userSex + "|" +modCus.userCellPhone;
                }
                return "0";
            }
        }