未捕获的SyntaxError:当我调用$(form)时，在0位置的JSON中意外的令牌u。

I have a form like this:

我有一个这样的表格:

<div class="row">
    @using (Ajax.BeginForm("ImportFromExcel", "QuanLySim", null, new AjaxOptions
                    {
                        UpdateTargetId = "div-form-daily",
                        HttpMethod = "POST",
                        OnBegin = "QuanLyDaiLy.BeforeSend",
                        OnFailure = "QuanLyDaiLy.Error",
                        OnComplete = "QuanLyDaiLy.Success",
                        InsertionMode = InsertionMode.Replace
                    }, new { @class = "form-update", @role = "form", @id = "search-form" }))
    {
        <div class="col-xs-12 col-sm-12 col-md-12">
            <div class="col-xs-12 col-sm-12 col-md-12">
                <div class="form-group">
                    <label for="so-ct" class="col-xs-12 col-sm-12 col-md-2 input-sm">File excel <span class="text-red required">*</span></label>
                    <div class="col-xs-12 col-sm-12 col-md-10 input-sm">
                        @Html.TextBoxFor(model => model.File, new { type = "file", accept = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet, application/vnd.ms-excel", @class = "btn btn-default btn-sm", style = "width: 100%;" })
                    </div>
                    <div class="col-xs-12 col-sm-12 col-md-2"></div>
                    <div class="col-xs-12 col-sm-12 col-md-10 color-red" style="padding-left: 10px; margin-top: 10px">
                        @Html.ValidationMessageFor(model => model.File)
                    </div>
                    <div class="clear"></div>
                </div>
            </div>
            <div class="col-xs-12 col-sm-12 col-md-12">
                <div class="form-group">
                    <label for="so-ct" class="col-xs-12 col-sm-12 col-md-2 input-sm">Giá nhân thêm</label>
                    <div class="col-xs-12 col-sm-12 col-md-10 input-sm">
                        @Html.TextBoxFor(model => model.Rate, new { @class = "form-control input-sm", placeholder = "Nhập tỷ giá cho giá sim..." })
                    </div>
                    <div class="col-xs-12 col-sm-12 col-md-2"></div>
                    <div class="col-xs-12 col-sm-12 col-md-10 color-red" style="padding-left: 10px; margin-top: 10px">
                        @Html.ValidationMessageFor(model => model.Rate)
                    </div>                     

                </div>
            </div>

            <div class="col-xs-12 col-sm-12 col-md-12">
                <div class="form-group">
                    <label for="so-ct" class="col-xs-12 col-sm-12 col-md-2 input-sm">Chọn đại lý <span class="text-red required">*</span></label>
                    <div class="col-xs-12 col-sm-12 col-md-10 input-sm">
                        @Html.DropDownListFor(model => model.AgentId, (IEnumerable<SelectListItem>)ViewBag.Agents, "Chọn...", new { @class = "form-control input-sm add-daily-sim filter-select" })
                    </div>
                    <div class="col-xs-12 col-sm-12 col-md-2"></div>
                    <div class="col-xs-12 col-sm-12 col-md-10 color-red" style="padding-left: 10px; margin-top: 10px">
                        @Html.ValidationMessageFor(model => model.AgentId)
                    </div>
                    <div class="clear"></div>
                </div>
            </div>
            <div class="col-xs-12 col-sm-12 col-md-12">
                <div class="form-group">
                    <label for="so-ct" class="col-xs-12 col-sm-12 col-md-2 ">Đảm bảo đã đúng giá?</label>
                    <div class="col-xs-12 col-sm-12 col-md-1">
                        @Html.CheckBoxFor(model => model.IsSure.HasValue)
                    </div>
                    <label for="so-ct" class="col-xs-12 col-sm-12 col-md-2 ">Xóa sim đại lý</label>
                    <div class="col-xs-12 col-sm-12 col-md-1 ">
                        @Html.CheckBoxFor(model => model.IsXoaSimCu.HasValue)
                    </div>
                </div>
            </div>

            <div class="col-xs-12 col-sm-12 col-md-12 text-center">
                <div class="form-group">
                    <button type="button" class="btn bg-maroon btn-cons btn-sm" id="btn-import-excel">
                        <i class="fa fa-floppy-o fa-lg"></i>&nbsp; Lưu
                    </button>
                    <button class="btn btn-default btn-sm" type="button" onclick="location.href='/[email protected]("Index", "QuanLySim")'"><i class="glyphicon glyphicon-refresh fa-lg"></i>&nbsp; Quay về</button>
                </div>
            </div>
        </div>
    }
</div>
<div cl