如何在前台脚本通过json传递数据到后台(使用微软自带的ajax)

function Save() {

            var examId = '<%=ExamId %>';

            var yearTerm = $("#<%=DDLYearTerm.ClientID %>").val();

            var examType = $("#<%=DDLExamType.ClientID %>").val();

            var examDate = $("#ExamDate").val();

            var examName = $("#ExamName").val();

            var exam = {};
            exam["ExamId"] = examId;
            exam["YearTerm"] = yearTerm;
            exam["ExamType"] = examType;
            exam["ExamDate"] = examDate;
            exam["ExamName"] = examName;
            var json = $.toJSON(exam);
            var Result = AjaxController.EditExam(json).value;
            if (Result == "Success")
            {
                alert("保存成功");
                parent.$.fancybox.close();
            }
            else
            {
                alert(Result);
            }
        }

protected void Page_Load(object sender, EventArgs e)

        {

            Ajax.Utility.RegisterTypeForAjax(typeof(Youjiao.xxt.BLL.Controller.AjaxController));

            if (!IsPostBack)

            {

                Databind();

            }

        }

[Ajax.AjaxMethod]
        public string EditExam(string value)

        {

            string Result = "";

            try

            {

                if (HttpContext.Current.Request.IsAuthenticated)

                {

                    EditExam editExam = JsonSerializeHelper.DeserializeFromJson<EditExam>(value);

                    ExamController eController = new ExamController();

                    eController.EditExam(editExam);

                    Result = "Success";

                }

                else

                {

                    Result = "会话无效，请重登录！";

                }

            }

            catch (Exception ex)

            {

                Result = ex.Message;

            }

            return Result;

        }

[Serializable]
    public class EditExam

    {

        public string ExamId { get; set; }

        public string YearTerm { get; set; }

        public string ExamType { get; set; }

        public string ExamDate { get; set; }

        public string ExamName { get; set; }

    }