layui upload 後臺獲取不到值

後臺獲取不到值方法一：

<script>
    layui.use('upload', function () {
        var upload = layui.upload;

        //執行實例
        var uploadInst = upload.render({
            elem: '#test1' //綁定元素
            , url: '/Home/UploadFiles' //上傳接口
             , field: "fileNames"     //添加這個屬性與後臺名稱保存一致
            , accept: 'file' //容許上傳的文件類型
            , size: 500000 //最大容許上傳的文件大小
            , before: function (obj) { //obj參數包含的信息，跟 choose回調徹底一致，可參見上文。
                layer.load(); //上傳loading
            }
            , done: function (res) {
                //上傳完畢回調
                alert(res.tc);
            }
            , error: function () {
                //請求異常回調
            }
        });
    });
</script>

 

 public ActionResult UploadFiles(HttpPostedFileBase fileNames)
        {
            string path = "";
            //小於20M
            if (fileNames.ContentLength > 0 && fileNames.ContentLength <= 120971520)
            {

                var fileName = Path.GetFileName(fileNames.FileName);

                string q_FN = fileName.Substring(0, fileName.LastIndexOf("."));
                string h_FN = fileName.Substring(fileName.LastIndexOf("."));

                string NewFileName = q_FN + DateTime.Now.ToString("yyyyMMddHHmmss") + h_FN;

                path = Path.Combine(Server.MapPath("/Uploadfile/"), NewFileName);
                fileNames.SaveAs(path);


                path = "/Uploadfile/" + NewFileName;
                var relt = new { tc = path };
                return Content(JsonConvert.SerializeObject(relt));
            }
            else
            {
                var relt = new { tc = "上傳文件要小於20M" };
                return Content(JsonConvert.SerializeObject(relt));
            }
        }