Prevenir que la session expire

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

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Timer ID="Timer1" runat="server" Interval="600000"/>
</ContentTemplate>
</asp:UpdatePanel>



http://csharpdotnetfreak.blogspot.com/2012/07/avoid-prevent-session-timeout-in-aspnet-keep-alive.html