ajax calendar extender not working in master page website

hello,
i have a master page website where i am trying to add ajax calendar control extender...but it is not working at all in master page...and i have added script manager control in my .master but still not working....my aspx page as follows

<%@ Page Language="C#" MasterPageFile="~/nationalmaster.master" AutoEventWireup="true" CodeFile="monthlytarget.aspx.cs" Inherits="monthlytarget" Title="Untitled Page" %>

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %>
<%@ Register Assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
    Namespace="System.Web.UI" TagPrefix="asp" %>

<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
    
<br />
    
    <br />
    
    <br />
    <br />
    State &nbsp; &nbsp;
    <asp:DropDownList ID="DropDownList1" runat="server">
    </asp:DropDownList>
    &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; project name &nbsp; &nbsp; &nbsp;&nbsp;
    <asp:DropDownList ID="DropDownList2" runat="server">
    </asp:DropDownList><br />
 
    <br />
    starting date &nbsp; &nbsp;
    <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
    &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
    &nbsp; &nbsp; end date &nbsp;
    &nbsp;
    <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox><br />
    &nbsp;<br />
    <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" /><br />
    <br />
    <cc1:CalendarExtender ID="CalendarExtender1" runat="server" TargetControlID="TextBox1">
    </cc1:CalendarExtender>
    <br />
    <asp:GridView ID="GridView1" runat="server">
    </asp:GridView>