jQuery OnChange function not working for ASP.Net DropDownList

Hi

The below code is not working, pl find the error

Thanks is advance.

<script type="text/javascript">
        $(document).ready(function () {
            $('#DropDownList2').change(function () {
                if (this.value == "Leave") {
                    $('#Leave').show();
                } else {
                    $('#Leave').hide();
                }

            });
        });

    </script>

<select name="DropDownList2" id="select2">
                    <option value="Select">Select</option>
                    <option value="Leave">Leave</option>
                    <option value="CO">CO</option>
     </select>