Getting the value from viewstate, in case the session expires

Question

I have a lot of pages in my project. In all pages I write:

if (!IsPostBack)
{     
   if (HttpContext.Current.Session["curUserRole"] == null)
   {
      DBUsers.SetUserStatusOnline("0", ViewState["curUserLogin"].ToString());
      ViewState["curUserLogin"] = "";
      Response.Redirect("~/Login.aspx");
   }
   else
   {       
      ViewState["curUserLogin"] = HttpContext.Current.Session["curUserLogin"].ToString();
      DBUsers.SetUserStatusOnline("1", ViewState["curUserLogin"].ToString());
   }
}

When a user logs in on the site, the current user role is written into the session and the current user login is written in the viewstate. When the session finishes, I thought that I could view the current user login in the viewstate and set the offline status in the database. But when session is null, the viewstate also null. What can I do?

score 2 · Answer 1 · answered May 23 '12 at 13:14

2

If Response.redirect is used, then ViewState cannot be accessed across pages. try using Server.transfer

check Access ViewState Across Pages for more information.

answered May 23 '12 at 13:14

Damith

62,401
13
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score 1 · Answer 2 · edited May 23 '17 at 11:49

Wouldn't using Forms Authentication be a better approach rather than manually handling roles, viewstate and session?

That way you'd interact with the current Identity to get user information, rather custom storage of information.

And I think you probably shouldn't depend on a postback by the user to determine if the session has expired. What if the user simply closes the browser? He/she would remain "Online" indefinitely.

You should provide a mechanism for the user to manually log out.

Now, if you are using InProc for your session state you can handle Session_End in global.asax to set that user to "Offline" in your database. If you are using StateServer or SQLServer then Session_End is not called on timeout, and you have to handle it in a custom way, such as through a scheduled task on the DB Server to mark users as Offline.

Now, if you really need a very precise control of the Online/Offline status, you might need to go for a more complex approach. One option would be, that whenever a user executes any action, to store a datetime on that last activity on the User table. And consider any user that hasn't done any activity in a specific time to be offline. Another option would be ajax calls used as a keep-alive call to update that datetime mentioned above.

CAbbott · Accepted Answer · 2012-05-23T13:21:12.340

0

In addition to UnhandledException's answer, I would also add that it might be better to centralize your logic in a class and then derive your pages from that new class rather than cut-and-pasting it to every page:

public class MyPageClass : System.Web.UI.Page
{
    protected override void OnLoad(EventArgs e)
    {
        // Add your logic here.

        base.OnLoad(e);
    }
}

public class WebPage1 : MyPageClass
{  
    private void Page_Load(object sender, System.EventArgs e)
    {
    }
}

edited May 23 '12 at 13:21

answered May 23 '12 at 12:59

CAbbott

8,078
4
31
38

ok. How I can save user login and call this method when any page reload and session is null? – Darien Fawkes May 23 '12 at 13:29
My answer was a suggestion on how to centralize your logic rather than cut-and-pasting it to every page. You need to look at `UnhandledException`'s answer for addressing the issue of a null `ViewState` when redirecting from another page. – CAbbott May 23 '12 at 13:35
@DarienFawkes - While I appreciate the rep, I don't think my answer solves your problem. Didn't `UnhandledException`'s answer fix your issue? If so, you should really accept his answer. – CAbbott May 23 '12 at 13:49

Getting the value from viewstate, in case the session expires

3 Answers3