HttpPostedFileBase在mvc asp.net中始终为null

Question

你好每个身体我在我的项目中使用bootstrap向导用html表单在里面我使用MVC Html.BeginForm我发布数据并且工作正常没有任何问题，除非我添加多个up-loader我总是得到它的空文件，但发布其他数据是好的，当我删除它上传的html表单标签工作，但向导停止这是我的试用，如果有任何建议？

<div class="tabbable-line tabbable-full-width" id="form_wizard_1">


<form class="form-horizontal" action="#" id="submit_form" method="POST">


    <div class="tab-content">

        <div class="alert alert-danger display-none">
            <button class="close" data-dismiss="alert"></button> text
        </div>



        <div class="row profile-account">

            <div class="col-md-3">


                        <ul class="ver-inline-menu tabbable margin-bottom-10">
                            <li class="active">
                                <a data-toggle="tab" href="#tab1">
                                    <i class="fa fa-cog" style="padding:0px;"></i> upload
                                </a>
                                <span class="after"> </span>
                            </li>
                            </ul>
                </div>
                            @using (Html.BeginForm("Home", "postdata", FormMethod.Post, new { enctype = "multipart/form-data" }))
                            {
                                @Html.AntiForgeryToken()
                                @*@Html.ValidationSummary("", new { @class = "text-danger" })*@
                                <div class="tab-pane" id="tab1">

                                    <div class="row">
                                        <div class="col-md-12">

                                            <div class="m-heading-1 border-green m-bordered">
                                                <h3>add files</h3>

                                            </div>
                                        </div>
                                    </div>

                                    <div class="m-heading-1 border-after-green-steel m-bordered" style="margin-top:20px;">
                                        @for (int i = 0; i < 4; i++)
                                        {
                                            @Html.TextBoxFor(x => x.files, new { type = "file", @class = "form-control" })<br />

                                        }
                                    </div>
                                </div>
                            }
                    </div>

                </div>
</form>
    </div>

<div class="form-actions">
    <div class="row">
        <div class="col-md-offset-3 col-md-9" style="margin-top: 20px;">
            <a href="javascript:;" class="btn default button-previous">
                <i class="fa fa-angle-left"></i> back
            </a>
            <a href="javascript:;" class="btn btn-outline blue button-next">
                go on
                <i class="fa fa-angle-right"></i>
            </a>
            <button type="submit" class="btn blue button-submit">
                save
                <i class="fa fa-check"></i>
            </button>

        </div>
    </div>
</div>