ASP.NET MVC 上传文件


<script src="../../Scripts/JQuery/jquery-1.5.1.js" type="text/javascript"></script>
<script src="../../Scripts/formValidator/formValidator-4.1.1.js" type="text/javascript" charset="UTF-8"></script>
<script src="../../Scripts/lhgdialog/lhgdialog.min.js?s=default" type="text/javascript"></script>
<script src="../../Scripts/lhgdialog/lhgcalendar.min.js" type="text/javascript"></script>
<script type="text/javascript">
$(document).ready(function(){
Page_Init();
});
$(document).resize(function(){Page_Init();});function Page_Init(){
    var intDistant_Left = $("#menu").offsetHeight;
    var intDistant = $("#main").offsetHeight - 205;
    if (intDistant > 0 && intDistant > intDistant_Left) $("#menu").style.height = intDistant + "px";
 }
 function GetHtmlInfo(_url)
 {
    var _http=_url;
    $.ajax({
    url:_http,
    context:document.body,
    success:function(data){
     $("#dataInfo").html(data);
    }
    });
 }
</script>   <li id="Li_upload"><a  href="javascript:GetHtmlInfo('/PersionalCenter/CoursewareUpload')"  >Courseware upload</a></li>  <div id="dataInfo">
       
   </div>----------------这个是加载页面里面的内容<script>
  $(document).ready(function () {
            $('#btn_Submit').click(function () {                $.ajax({
                    url: '/PersionalCenter/CoursewareUpload',
                    data: $('#courseForm').serialize(),
                    type: 'POST',
                    beforeSend: function () {  },
                    success: function (data) {
                        alert(data);
                    }
                });            });
        });
</script>
  <% Html.BeginForm(null, null, FormMethod.Post, new { name = "courseForm", id = "courseForm", enctype = "multipart/form-data" }); %> <input type="file" name="mar" id="file_img"  style="width: 179px; border: 1px solid #aaa;"  />
      <input type="button" id="btn_Submit" name="btn_Submit" value="Submit" />
  <% Html.EndForm();%>  [AcceptVerbs(HttpVerbs.Post)]
        public ActionResult CoursewareUpload(HttpPostedFileBase Files, TSD_C_Courseware courseware)
        {
int requestBase=    Request.Files.Count;
string fileName = Request.Files[0].FileName;
return View();
}求为什么  我点提交的时候在Controller 里获取不到这个Input File 的内容呢.