ASP.NET MVC级联下拉列表使用AJAX返回未定义的返回

Question

我试图为类和主题列出级联下拉列表时，当我从下拉列表中选择一个类时，主题下拉列表显示了响应类中的主题。 但是，控制器中返回的主题价值是（未定义）

这是我的观点

<div class="form-group">
        @Html.LabelFor(model => model.PDFClass, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownListFor(model => model.PDFClass, ViewBag.ClassName as SelectList, "Please Select", new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.PDFClass, "", new { @class = "text-danger" })
           
        </div>
    </div>




    <div class="form-group">
        @Html.LabelFor(model => model.PDFSubject, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownListFor(model => model.PDFSubject, new SelectList(" "), "Please Select", new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.PDFSubject, "", new { @class = "text-danger" })
            
        </div>
    </div>

这是Ajax

  <script>
        $(document).ready(function () {
            $("#PDFClass").change(function () {

                $.get("/Home/GetStateList", { Class: $("#PDFClass").val() }, function (data) {
                    $("#PDFSubject").empty();
                    $.each(data, function (index, row) {
                        $("#PDFSubject").append("<option value = '" + row.Class + "'>" + row.SubjectName + "</option>")
                        debugger;
                    });
                });
            })
        });
    </script>

这是该方法获得类＆amp; amp;受试者的关系表与Ajax

        public JsonResult GetStateList(string Class)
        {

            var List1 = context.ClassesWithSubjects_.ToList().Where(i => i.ClassName == Class);
            return Json(List1, JsonRequestBehavior.AllowGet);
        }