将变量从java脚本传递给aspx表单

Question

我想将变量数据从js发送到我的aspx web表单

这是我的HTML

          <select id="DDL_WorkCategory" class="form-control select2" multiple="multiple" data-placeholder="Select a Category" style="width: 100%;" onchange="myfunction();">
                                <option>نحت</option>
                                <option>خزف</option>
                                <option>تصميم</option>
                                <option>تصوير</option>
                                <option>تشكيل</option>
                                <option>ترمييم</option>
                            </select>  <input type="hidden" ID="hidden_WorkCategory" runat="server"  />

这是js

          <script>
    $("form").submit(function () {
        GetSelectedValues();
    });
    function GetSelectedValues() {
        var data = $("#DDL_WorkCategory").val();
        alert(data);
        var hiddenControl = '<%= hidden_WorkCategory.ClientID %>';
        document.getElementById(hiddenControl).value = data;


    }

</script>

这是css

             protected void Submit_Click(object sender, EventArgs e)
    {

        string x = hidden_WorkCategory.Value;
     }

字符串没有值仍然为空