calender extender not working in ASP.NET

I am trying to add

Calender Extender using AJAX

on my web application. I am trying to popup calnder on click of textbox I have tried all steps as mentioned here in this example

I have redownloaded AJAX TOOLKIT 4.5 and psted it in bin folder. But nothing happens my codes are

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="ajax" %>

.

<asp:TextBox ID="txtfrom" runat="server"></asp:TextBox>
<ajax:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server"></ajax:ToolkitScriptManager>
<ajax:CalendarExtender ID="CalendarExtender1" runat="server" TargetControlID="txtfrom" PopupButtonID="txtfrom"></ajax:CalendarExtender>

So let me know what I a missing here.

Thanks