Request.Files is always null

我正在编写一个C#ASP.Net MVC应用程序，用于客户端将文件发布到其他服务器。我正在使用一个通用处理程序来处理从客户端到服务器的已发布文件。但在我的处理程序中，System.Web.HttpContext.Current.Request.Files始终为空（0计数）。

表单代码：

@model ITDB102.Models.UploadFileResultsModels
@{
    Layout = "~/Views/Shared/_Layout.cshtml";
}
<div>
    <h1>Upload File</h1>
    <form id="file-form" action="/Files/UploadFile" method="post" data-ajax="false" enctype="multipart/form-data">
        <div><input type="file" id="FilePath" name="FilePath"/>
        <button type="submit">Send File</button></div>
    </form>
</div>
@section scripts{
    <script src="~/Scripts/jquery-1.10.2.js"></script>
    <script type="text/javascript">
        // Variable to store your files
        var files;
        var form = document.getElementById('file-form');
        // Add events
        $('input[type=file]').on('change', prepareUpload);
        // Grab the files and set them to our variable
        function prepareUpload(event) {
            files = $('#FilePath').get(0).files;
        }
        form.onsubmit = function (event) {
            uploadFiles(event);
        }
        // Catch the form submit and upload the files
        function uploadFiles(event) {
            event.stopPropagation(); // Stop stuff happening
            event.preventDefault(); // Totally stop stuff happening           
            // Create a formdata object and add the files
            var data = new FormData();
            if (files.lenght > 0)
            {
                data.append('UploadedFiles', files[0], file[0].name);
            }
            //setup request
            var xhr = new XMLHttpRequest();
            //open connection
            xhr.open('POST', '/Files/UploadFile',false);
            xhr.setRequestHeader("Content-Type", files.type);
            //send request
            xhr.send(data);
        }
    </script>
}

经办人：

/// <summary>
    /// Uploads the file.
    /// </summary>
    /// <returns></returns>
    [HttpPost]
    public virtual ActionResult UploadFile()
    {
        HttpPostedFile myFile = System.Web.HttpContext.Current.Request.Files["UploadedFiles"];
        bool isUploaded = false;
        string message = "File upload failed";
        if (myFile != null && myFile.ContentLength != 0)
        {
            string pathForSaving = Server.MapPath("~/Uploads");
            if (this.CreateFolderIfNeeded(pathForSaving))
            {
                try
                {
                    myFile.SaveAs(Path.Combine(pathForSaving, myFile.FileName));
                    isUploaded = true;
                    message = "File uploaded successfully!";
                }
                catch (Exception ex)
                {
                    message = string.Format("File upload failed: {0}", ex.Message);
                }
            }
        }
        return Json(new { isUploaded = isUploaded, message = message }, "text/html");
    }

    #region Private Methods
    /// <summary>
    /// Creates the folder if needed.
    /// </summary>
    /// <param name="path">The path.</param>
    /// <returns></returns>
    private bool CreateFolderIfNeeded(string path)
    {
        bool result = true;
        if (!Directory.Exists(path))
        {
            try
            {
                Directory.CreateDirectory(path);
            }
            catch (Exception)
            {
                /*TODO: You must process this exception.*/
                result = false;
            }
        }
        return result;
    }
    #endregion

请帮帮我。谢谢。