kendo组合框过滤无法正常工作

Question

我已经实现了kendo组合框控件并尝试实现了filter选项。我正在显示的文本字段是连接字段。我有 设置以下属性，但过滤似乎不起作用。当用户键入前几个字符时，它应该过滤记录

.Filter("contains")
.ServerFiltering(true)

它对我的其他包含连接字段的组合框也不起作用。我错过了什么

 <div class="col-md-4">
                <div class="form-group">
                    @Html.LabelFor(model => model.Company, htmlAttributes: new { @class = "control-label col-md-4" })
                    <div class="col-md-8">
                        <div class="editor-field">
                            @(Html.Kendo().ComboBoxFor(model => model.CountryCode)
                            .HtmlAttributes(new { style = "width:100%" })
                            .DataTextField("CompanyCodeCompany")
                            .DataValueField("CountryCode")
                            .Filter("contains")
                            .MinLength(3)
                            .Events(e => e.DataBound("onCompanyComboChange"))
                            .Value(@user.DefaultCountryCode)
                            .DataSource(dataSource => dataSource
                            .Read(read => read.Action("RequestHeader_SalesOrganisation", "Request").Type(HttpVerbs.Post))
                            .ServerFiltering(true)
                            )
                            )
                        </div>
                        @Html.ValidationMessageFor(model => model.Company, "", new { @class = "text-danger" })
                    </div>
                </div>

控制器

  public ActionResult RequestHeader_SalesOrganisation()
        {
            var response = requestRepository.GetSalesOrganisation().AsQueryable().ProjectTo<SalesOrganisationViewModel>();

            var jsonResult = Json(response, JsonRequestBehavior.AllowGet);
            jsonResult.MaxJsonLength = int.MaxValue;
            return jsonResult;
        }