Hidden button still required for Modal popup extender?

I have used the AJAX Control Toolkit in a few years.  Is a button like the one below still required for the Moday Popup extender to work?

<ajax:ModalPopupExtender ID="ModalPopupExtender" runat="server" TargetControlID="btnHidden" BehaviorID="MPBehavior1" 
PopupControlID="pnlModalPopUp" ></ajax:ModalPopupExtender><asp:Button ID="btnHidden" runat="server" Text="Button" style="display: none;" />