ASP.net 级联下拉列表

试图在 mvc 中实现国家/地区下拉菜单，但不能..

控制器：-

[HttpGet]
    public ActionResult GetCities(int StateId)
    {

        Business.Services.City cityService = new Business.Services.City();

        List<Business.Models.City> stateList = cityService.GetCityByStateId(StateId);

        //var jsonSerialiser = new JavaScriptSerializer();
        //var json = jsonSerialiser.Serialize(stateList);

        return Json(new { stateList }, JsonRequestBehavior.AllowGet);

    }

方法：

public List<Models.City> GetCityByStateId(int StateId)
        {
            try
            {
                var list = new List<SelectListItem>();

                Collection<DBParameters> parameters = new Collection<DBParameters>();
                parameters.Add(new DBParameters() { Name = "StateId", DBType = DbType.Int32, Value = StateId });
                var city = this.ExecuteProcedure<Models.City>("GetCityByState", parameters).ToList();

                //if (city != null && city.Count > 0)
                //{
                //    list = city.Select(x => new SelectListItem { Text = x.CityName, Value = x.StateId.ToString() }).ToList();
                //}

                return city;

            }
            catch (Exception ex)
            {
                throw;
            }
        }

更改事件：

 $('.ddlstate').change(function () {
    debugger;


    $.ajax({
        url: '@Url.Action("GetCities", "User")',
        type: "GET",
        data: { StateId: $(this).val() },
        dataType: "json",
        success: function (result) {
            debugger;
            //alert(result.stateList[0].CityId);
            $.each(result.stateList, function () {
                debugger;
                $('.cityddl').append($("<option></option>").val(CityId).html(CityName));
            });
        },
        error: function (result, status, jQxhr) {
            alert("Error: " + result + "-" + status + "-" + jQxhr);
        }
    });

});

我得到了方法和控制器中引用的计数，但是当我运行项目并更改状态下拉列表时，我得到了空白的城市下拉列表。怎么了？