<ajax:UpdatePanel ID="ajPnlUpdSegnalazioni" runat="server">
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="Timer1" EventName="Tick" />
        <asp:PostBackTrigger ControlID="gridview"/>
    </Triggers>
    <ContentTemplate>
       GRIDVIEW
    </ContentTemplate>
</ajax:UpdatePanel>
<ajax:Timer runat="server" ID="Timer1" Interval="60000" OnTick="Timer1_Tick"  EnableViewState="true"></ajax:Timer>
</asp:Content>