Prolonging asp.net session enddate?

Question

How is asp.net Session prolonging, does every request prolongs the end date of Session, and is it enough to call void() by ajax to extent Session end date by another period of time(default 20 min or so...)

public void ResetSessionTime()
{

}

or do i have to invoke session in some way:

public void ResetSessionTime()
{
    User currentUser = HttpContext.Current.Session[userSessionKey] as User;
}

how does simple request extend session end date?

This question claims every post-back prolongs session...

This MSDN about Session State Providers :

"Each session created by ASP.NET has a timeout value (by default, 20 minutes) associated with it. If no accesses to the session occur within the session timeout, the session is deemed to be expired, and it is no longer valid."

How does request access the session exactly?

THIS QUESTION: Keeping session alive C# does not answer how session end date is prolonged by request, only a opinion on how to keep session alive from client side

EDIT:

According to this article, method needs to be extended from IHttpHandler, in order to access current session...

public class KeepSessionAlive : IHttpHandler, IRequiresSessionState
{
    public void ProcessRequest(HttpContext context)
    {
        context.Session["KeepSessionAlive"] = DateTime.Now;
    }
}

Answer 1

Every time you make a request, the session timeout is reset. A request can be a page load or something like an ASYNC call.

Take a look at this question for an example of how to keep the session alive by periodically making AJAX calls to the server. (Keeping ASP.NET Session Open / Alive)