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
+6
A:
You can't really "push" a client from your website. Your site will respond to requests from the client, but that's really it.
What this means is that you need to write something client-side (Javascript) that will determine when the user has timed out, probably by comparing the current time with the most recent time they have in a site cookie (which you update with the current time each time the user visits a page on your site), and then redirect if the difference is greater than a certain amount.
(I note that some people are advocating just creating a script that will forward the user after a certain amount of time on a page. This will work in the simple case, but if the user has two windows open on the site, and is using one window a lot, and the other window not-so-much, the not-so-much one will suddenly redirect the user to the forwarding page, even though the user has been on the site constantly. Additionally, it's not really in sync with any session keeping you're doing on the server side. On the other hand, it's certainly easier to code, and if that's good enough, then great!)
Beska
2009-01-27 20:00:28
+1
A:
Unfortunately it can't be done. The session timeout only occurs on the server side and you won't detect this until the user performs some kind of post back action.
However, what you CAN do is to inject some HTML or JavaScript header code that will automatically push the user to a logout page in the same timeframe as your session timeout. This doesn't guarantee a perfect synch, and you may run into issues if your user is doing some time intensive items and you are not resetting the clock.
I typically add this code to my Page_Load events to accomplish this.
' Register Javascript timeout event to redirect to the login page after inactivity
Page.ClientScript.RegisterStartupScript(Me.GetType, "TimeoutScript", _
"setTimeout(""top.location.href = 'Login.aspx'""," & _
ConfigurationManager.AppSettings("SessionTimeoutMilliseconds") & ");", True)
Dillie-O
2009-01-27 20:01:24
A:
In the <HEAD> section, use a META refresh tag like this:
<meta http-equiv="refresh" content="0000; URL=target_page.html">
where 0000 is your session timeout in seconds, and target_page.html the address of the page to be redirected to.
devio
2009-01-27 20:03:03
+4
A:
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.
TJB
2009-01-27 20:03:42
A:
Does this redirects to target_page after 0000 seconds even if user actively performing some actions?
Raj
2010-03-18 16:41:13
Depends on the actions - if any of the actions resulted in a new page being sent back to the user, then the users timeout will have been reset as would the refresh counter. Otherwise the page will just redirect on that timeout. If you have some AJAX requests going back to the server, you'll need to be a bit cleverer: the session timeout will reset with each request, however there's nothing to update the page's meta tag, in that case you'd need to do the timeout management with an JavaScript timer that you can reset on successful requests.
Zhaph - Ben Duguid
2010-03-18 16:48:48