Why ajax rating control is not working?

See more:

C#

ASP.NET

Ajax

I have added a ajax rating control in page whose scripting code looks like this

<style type="text/css">
.Star
    {
        background-image: url(Images/Star.gif);
        height: 17px;
        width: 17px;
    }
    .WaitingStar
    {
        background-image: url(Images/WaitingStar.gif);
        height: 17px;
        width: 17px;
    }
    .FilledStar
    {
        background-image: url(Images/FilledStar.gif);
        height: 17px;
        width: 17px;
    }
<asp:Rating ID="Rating2" runat="server" CurrentRating="1" MaxRating="5"   
                StarCssClass="Star" WaitingStarCssClass="WaitingStar" 
EmptyStarCssClass="Star"
    FilledStarCssClass="FilledStar" OnChanged="Rating2_Changed" 
    AutoPostBack="True">
                        </asp:Rating> 

When I run it it is working mean showing me the star images on the page. But when I click on it to rate the stars it does nothing. I debug the code but it is entering in the Rating_Changed event. I'm using Visual Studio 2012, ASP.NET 4.5, and latest ajaxtoolkit 4.0 Kindly tell me why it is not working?