使用ajax将表单数据传递给控制器​​操作

Question

我正在使用ASP.NET MVC，我想将表单数据传递给我的操作，但我注意到传递后我的操作中变量file的值为null

public void ImgUpload(HttpPostedFileBase file)
    {
        bool isSavedSuccessfully = true;
        String fName = "";
        try
        {
            foreach (String filename in Request.Files)
            {
                file = Request.Files[filename];
                fName = file.FileName;
                if (file != null && file.ContentLength > 0)
                {
                    var originalDirectory = new DirectoryInfo(string.Format("{0}Images\\WallImages", Server.MapPath(@"\")));                 
                    bool isExists = Directory.Exists(originalDirectory.ToString());
                    if (!isExists)
                        Directory.CreateDirectory(originalDirectory.ToString());
                    var path = string.Format("{0}\\{1}", originalDirectory.ToString(), file.FileName);
                    file.SaveAs(path);

                }




            }


        }
        catch (Exception e)
        {

            isSavedSuccessfully = false;
        }

    }

表格还有这两个标签：

        <div class="form-group">
        <label class="control-label" for="file">Filename:</label>
        <div class="col-md-10">
            <input type="file" name="file" id="file" />
        </div>

    </div>
    <div class="col-md-10 col-md-offset-2">
        <input id="submit" type="submit" value="Create" class="btn btn-default" />
    </div>

这是功能：

        <script>
$('#submit').click(function (e) {
    e.preventDefault(); // <------------------ stop default behaviour of button
    var element = this;
    var formDataa = new FormData(this.form);
    $.ajax({
        url: "/ImageUploader/ImgUpload",
        type: "POST",
        data: JSON.stringify(formDataa),
        processData : false ,
        dataType: "json",
        traditional: true,
        contentType: "application/json; charset=utf-8",
        success: function (data) {
            if (data.status == "Success") {
                alert("Done");
                $(element).closest("form").submit(); //<------------ submit form
            } else {
                alert("Error occurs on the Database level!");
            }
        },
        error: function () {
            alert("An error has occured!!!");
        }
    });
});

</script>

实际上我正在尝试将文件上传到服务器，我认为我的问题是如何或者什么是处理发布数据的正确类型。