Question

I’m looking for a tutorial, blog entry, or some help on the technique behind websites that automatically push users (ie without a postback) when the session expires. Any help is appreciated

Answer 1

Usually, you set the session timeout, and you can additionally add a page header to automatically redirect the current page to a page where you clear the session right before the session timeout.

From http://aspalliance.com/1621_Implementing_a_Session_Timeout_Page_in_ASPNET.2

namespace SessionExpirePage {     public partial class Secure : System.Web.UI.MasterPage     {         public int SessionLengthMinutes         {             get { return Session.Timeout; }         }         public string SessionExpireDestinationUrl         {             get { return '/SessionExpired.aspx'; }         }         protected override void OnPreRender(EventArgs e)         {             base.OnPreRender(e);             this.PageHead.Controls.Add(new LiteralControl(                 String.Format('<meta http-equiv='refresh' content='{0};url={1}'>',                  SessionLengthMinutes*60, SessionExpireDestinationUrl)));         }     } } 

The SessionExpireDestinationUrl should link to a page where you clear the session and any other user data.

When the refresh header expires, it will automatically redirect them to that page.