转载http://www.cnblogs.com/luoyefeiwu/p/5776507.html，非常感谢该篇文章帮我解决了问题

1.前端请求如下

var apply = { CompanyName: $("[name='corpName']").val(),ContactUser: $("[name='contName']").val(),Address: $("[name='address']").val(),Mobile: $("[name='phone']").val(),MainProducts: $("[name='goods']").val(),Remark: $("[name='mark']").val(),IsMember: $("[name='Meber']:checked").val() };
            var applyDetail = [];
            $('.Info').each(function (index,item) {
                //参会代表
                var DelegateName = $(item).find("[name='Name']").val();
                //性别
                var Sex = $(item).find("[name='Sex']").val();
                //职位
                var Post = $(item).find("[name='Position']").val();
                //手机
                var Mobile = $(item).find("[name='Phone']").val();
                //邮箱
                var EMail = $(item).find("[name='Email']").val();
                //会场
                var SiteType = $(item).find("[name='SiteType']").val();
                var detial = { DelegateName: DelegateName,Sex: Sex,Post: Post,Mobile: Mobile,EMail: EMail,SiteType: SiteType };

                applyDetail.push(detial);
            });
            var postData = { applyModel: apply,applyDetail: applyDetail };
            $.ajax({
                url: '/ActivityBusiness/Apply_From_Json?ApplyNo=@ViewBag.ApplyNo&SpeciaNo=@ViewBag.SpeciaNo',data: JSON.stringify(postData),dataType: 'json',contentType: 'application/json',type: "POST",// traditional: true,success: function (res) {
                    if (res.Success) {
                        tipDialog(res.Message,3,res.Code);
                        top.frames[tabiframeId()].windowload();
                        closeDialog();
                    }
                    else {
                        tipDialog(res.Message,-1);
                    }

                }
            });

2，注意事项

要设置 contentType: 'application/json'