JQUERY FORM AjaxSubmit异步上传文件有关问题

JQUERY FORM AjaxSubmit异步上传文件问题
异步上传文件，使用了jquery.form ajaxSubmit，提交后，后台接受不到请求

 <script type="text/javascript">
 
        $(document).ready(function () {
            $("#Button1").click(function () {
if ($("#fileUp").val() =="")
                {
                    window.alert("It is not Empty！");
                    return false;
                }
                $("#form1").ajaxSubmit({
                    type: "post",
                    url: "Handler1.ashx",
                    dataType: "text",
                    data: { "filename": $("#Text1").val() },
                    success: function (data) {
                        window.alert(data);
                    },
                    error: function () {
                    }
                });
            });
        });
 </script>
<form id="form1" >
        <div>
            内容：<input type="text" id="Text1" /><br />
            文件：<input type="file" name="fileUp" id="fileUp" />
            <input id="Button1" type="button" value="上传" />
        </div>
    </form>


后台代码：
 public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/plain";
            int count = context.Request.Files.Count;
            string name = context.Request["filename"];
            HttpPostedFile hf = context.Request.Files["fileUp"];
            string fileName = DateTime.Now.ToString("yyyMMddHHmmss") + Path.GetExtension(hf.FileName);
            string url = context.Server.MapPath("~/Files/");
            hf.SaveAs(url+fileName);
            context.Response.Write("{\"status\":\"1\"}");
        }
------解决思路----------------------
文件本来就不能通过ajax上传，只能通过form data的方式submit
------解决思路----------------------
只能submit吧