Update Database after session timeout and browser closed.

I thing you should try this.

On the form_load event in every page, write the below code.

Response.AppendHeader("Refresh", "60; URL=../default.aspx")

Default session time out is 20 minutes and I am using "60" seconds for this demo. If there is no activity in this period of time, then it goes back to the default or home page and we send a key to update the database "session key" or any other tag. This way we can possibly know the activity of the user or member.

This worked for me. 

You can learn more about sessions here...

http://www.encodedna.com/2012/12/session-variable-in-asp.net-class.htm

refer an article, will get some idea.

 Yep, i tried that, session_end fires after the timeout time specified in my web.config. I also tried to put code inside session_end but it always go to application_error event.

I used session variables as my reference for updating my database table, but the problem is when timeout occurs my session variables are also gone. Any better idea for this?, Thanks in advance..

Session Timeout event can be handled in Session_End event in Global.asax page.
 
Browser Closed event can be handled in the OnUnload Event of the body tag in the aspx page.
 
Put your functionality to update the database in the above two events, that would solve your problem

See on this thread
http://www.c-sharpcorner.com/Forums/UploadFile/103930/