<asp:ScriptManager ID="ScriptManager1" runat="server">        </asp:ScriptManager>        <asp:UpdatePanel ID="UpdatePanel1" runat="server">            <ContentTemplate>                                    <asp:Timer ID="Timer1" runat="server" Interval = "1000"></asp:Timer>            <asp:UpdateProgress ID="UpdateProgress1" runat="server">                <ProgressTemplate >                圖片讀取中......                </ProgressTemplate>                </asp:UpdateProgress>            </ContentTemplate>        </asp:UpdatePanel>在每次定時刷新后，希望調(diào)用后臺的AA(),怎樣實現(xiàn)？