Sometimes you want your web page to ‘stay alive’. That is, if a user is filling out a complicated form, that may contain several fields, you do not want the session to time out before they are finished.

It’s not simply a matter of increasing the session timeout to a very large value. If you do that, the sessions would be left active in the server memory for hours—long after the visitors have left the site. Increasing the session timeout IS a solution… but not necessarily a good solution.

The goal is that the session should stay active as long as the web page is open on the client machine …even if there are no post backs to reset the session timer. When the web page is closed, the session should time out normally.

I implemented a solution for this: The client will “ping” the server at intervals of less than the session timeout which will reset the session timer. This is known as the Heartbeat design pattern

For testing purposes, I set the Session Timeout to two minutes in web.config:

<sessionState timeout=”2″></sessionState>

to trace the output of defferent events i used “System.Diagnostic.Debug” class.

To watch the Session State events, I added debugging strings to the global.asax file:


Here is what the output looks like without the heartbeat:


We need a method at the server for the client to call. We use a WebMethod.

  1. There must be a ScriptManager on the page.
  2. The ScriptManager must have EnablePageMethods set to true.
  3. The WebMethod must be public and static.
  4. The WebMethod must have the EnableSession attribute set to true.



Here is the output with the heartbeat:


It looks like the session is staying alive while the client is idle: Excellent!

I hope someone finds this useful.

if this is helpful, dont forget to leave a comment.