Programmatically show hide AJAX "PopupControlExtender"

how to show/hide popupextender through C#

in aspx page 

<asp:Panel ID="divPopup" runat="server" CssClass="DivPopup"></asp:Panel>

   <ajaxToolkit:PopupControlExtender ID="PopupExtndr" runat="server" PopupControlID="divPopup"  TargetControlID="fakeButton"    BehaviorID="popupBhvr">

use following javascript syntax to show hide PopupControlExtender:

 $find('popupBhvrPopupBehavior').hide();

 $find('popupBhvr').showPopup();