ajax popupcontrolextender

I have created one web application in asp.net to show calendar control as popup.. i have written the code for PopupControlExtender but it shows the error as unrecognized tag prefix for

   <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>

</div>
<asp:TextBox ID="TextB开发者_运维问答ox1" runat="server"></asp:TextBox>
<br />
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
        <asp:Calendar ID="Calendar1" runat="server"></asp:Calendar>
    </ContentTemplate>
</asp:UpdatePanel>

<ajax:PopupControlExtender ID="PopupControlExtender1" runat="server" TargetControlID="TextBox1" 
   PopupControlID="Panel1" 
   Position="Right" 
   CommitProperty="value" 
   OffsetX="3"> 

Make sure you include the AjaxControlToolkit, in order to be able to use only of it's controls.

I'm unsure as to which .NET version you are using, but essentially you need to reference the dll in your project, then add the following at the top of your code, after the first page declaration.

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="ajax" %>
<asp:Content ID="Content1" runat="server" ContentPlaceHolderID="head">

If you are using .NET 3.5 toolkit, then that's all you should require. In .NET 4 toolkit, it's best that you replace your asp:ScriptManager with the asp:ToolkitScriptManager.

You can get the toolkits here