Question: hello i want to apply css for nav bar, i am retrivig nav bar values from database using Ajax.ActionLink, i tried javascript but i am getting error called 

> 
> jQuery is not defined",
> 
> 
> 

here is my code. and Test\_Section is my Model. 

```
<table style="width:auto">    
    @foreach (Test_Section p in Model)
    {
        <tr>
            <td>
                <div id="ajaxnav" class="navbar-left">
                    <ul class="nav nav-tabs nav-stacked">
                        <li>
                            @Ajax.ActionLink(p.SectionName, p.Title, new { id = p.StdSectionId , @class = "navigationLink"},
                   new AjaxOptions
                   {
                       UpdateTargetId = "getHtml",
                       InsertionMode = InsertionMode.Replace,
                       HttpMethod = "GET"
                   }, new { style = "color:#428bca" ,  @class = "navigationLink"  })

                        </li>
                    </ul>
                </div>
            </td>
        </tr>

    }
</table>

<script type="text/javascript">
    $('.navigationLink').click(function () {
        $('.navigationLink').removeClass('active');   
        $(this).addClass('active');  
    });
</script>

```

Please help me.

Answer: 
You need to include jQuery to your application by referencing it in your page, because the Error `jQuery is not defined` or `$ is not defined` occurs when jQuery is not (correctly) included in your page.
You should add this line before the `<script>` section in your posted code:

```
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.0/jquery.min.js"></script>

```

Hope this help you.
You need to use `.click` inside

```
  $(document).ready(function(){//...onclick(...)})

```

But first make sure, you include jquery script file in your html.