I have below code. what I am trying to do is apply the CSS class from code behind c# with javascript only without using runat server attribute.

In the code behind, I am using below script, but it is not adding the class active. What I am doing wrong here?

C# Code behind:

```
ScriptManager.RegisterStartupScript(this, typeof(string), "script", 
    "<script type=text/javascript> $('#pendingtask').addClass('tab-pane fade in active');</script>", 
    false);

```

View/page:

```
<div class="tab-pane fade in" id="pendingtask">
   <div class="row col-sm-12">
      <div>
         <asp:UpdatePanel ID="UpPending"  runat="server">
            <ContentTemplate>
               <asp:ListView ID="lvPendingTask" runat="server" DataKeyNames="EXV_KEY" OnItemCommand="lvPendingTask_ItemCommand" OnItemDataBound="lvPendingTask_ItemDataBound">
                  <LayoutTemplate>
                     <table id="datatable_fixed_column" class="table-striped table-hover table-responsive table-bordered table-condensed" width="100%">
                        <thead>
                           <tr>
                              <th style="width: 30px">ID</th>
                              <th>Task</th>
                              <th>Stage</th>
                              <th>Status</th>

                              <th style="width: 120px">Options</th>
                           </tr>
                        </thead>
                        <tbody>
                           <tr id="itemplaceholder" runat="server"></tr>
                        </tbody>
                     </table>
                  </LayoutTemplate>
                  <ItemTemplate>
                     <tr>
                        <td>
                           <asp:Label ID="lblID" runat="server" Text='<%#Eval("EXV_KEY") %>'></asp:Label>
                        </td>
                        <td><%#Eval("TASK_DESC")%></td>
                        <td><%#Eval("STAGE_DESC")%></td>
                        <td><%#Eval("ts_desc_eng")%></td>

                        <td>
                           <asp:LinkButton ID="lbtnPrint" class="btn btn-xs btn-info" Visible="False"  CommandName="PrintLetter" runat="server"  OnClientClick="showOverlay();"> Print</asp:LinkButton>
                           <asp:LinkButton ID="lbtnCompleteTask" class="btn btn-xs btn-info" Visible="False" CommandName="CompleteTask" runat="server"  OnClientClick="showOverlay();"> Mark Complete</asp:LinkButton>
                           <asp:LinkButton ID="lbtnEdit" class="btn btn-xs btn-danger" Visible="False" CommandName="EditTask" runat="server"  OnClientClick="showOverlay();"> Edit</asp:LinkButton>
                           <asp:LinkButton ID="lbtnDelete" class="btn btn-xs btn-danger" Visible="False" CommandName="Delete" runat="server"> Delete</asp:LinkButton>
                        </td>
                     </tr>
                  </ItemTemplate>
                  <EmptyDataTemplate>
                     <p> 
                     <h5><span class="label label-danger">No Record Found!  </span></h5>
                     </p>
                  </EmptyDataTemplate>
               </asp:ListView>
               <!-- end widget content -->
            </ContentTemplate>
         </asp:UpdatePanel>
      </div>
      <div class="col-sm-12">
         <hr/>
      </div>
   </div>
</div>

```