asp.net gridview links seem to be "expiring" - how to stop?

Question

I have an ASP.NET 3.5 page with a gridview databound to a generic list of objects. The purpose of this page is to show the user a list of items they're responsible for so they can select one and go to the maintenance page to see the details of that item.

I have the "AutoGenerateSelectButton" property set to True. I have no problem when the user immediately selects one of the items (firing the .SelectedIndexchanged event, I do a little processing and Response.Redirect them to the appropriate page).

However, if I wait a few minutes, then hit the Select, I get "Cannot display the webpage" as if I were disconnected from the net. No messages get sent to the application's log file (debugging messages that should indicate the user selected a particular item and that a redirect is about to happen) so there's nothing for me to trap/debug/fix.

I tried going into the web.config and added

"<sessionState timeout="60"></sessionState>"

in hopes that the timeout would go to an hour (users will frequently let the app sit on their screens for quite a while) but that doesn't seem to have worked.

Where else can I look?

Thanks in advance

Answer 1

I've had a very similar issue. You may hate this answer because it's a little tedious but I programmatically added a button in the Gridview_RowCreated which allows more power.

On page load add a column to the grid.

 If Not IsPostBack Then
        Dim field As New TemplateField
        field.HeaderText = "Maintenance"
        Dim col As DataControlField = field
        GridView.Columns.Add(col)

--Add the link button here

For i = 0 To GridView.Rows.Count - 1
            Dim alinkbutton As New Linkbutton
            GridViewCshr.Rows(i).Cells(3).Controls.Add(alinkbutton )
        Next
 End If

(adding the button to the grid is in the third column but add it whereever you add the new column programmatically)

---Then in GridView_rowcommand

Response.Redirect("url")

Answer 2

I can see from your web.config extract that you are running your sessionState in process (Default mode). In this mode the session state is effectively kept in memory in the process of the IIS worker process. This means that when the IIS Worker process handling your application is terminated, e.g. because IIS is recycling the application pool, the session state is wiped out.

You can try increasing the idle time out for the worker process ( the default is 20 minutes ) on the application pool configuration.

For IIS6

1. In IIS Manager, expand the local computer, expand Application Pools, right-click the application pool, and then click Properties.
2. On the Performance tab, under Idle timeout, deselect the Shutdown worker processes after being idle for check box. -OR-
3. In the minutes box, type the number of idle minutes (with no processing requests) that you want to elapse before shutting down the idle worker process. The default value is 20 minutes
4. Click OK.

For IIS7

1. Open inetmgr
2. Expand the appropriate server
3. Click "Application Pools"
4. Right click the Application Pool Under which your application is running and from the context menu select "Recycling"
5. Deselect all checkboxes, click "Next" and click "Finish"
6. Right click the Application Pool Under which your application is running and from the context menu select "Advanced Settings ..."
7. Under "Process Model" set "Idle Time-Out (minutes)" to some large value
8. Click "OK"

However, it would be far better to move your session state out of process for long running applications such as yours. It is a fairly simple procedure and will save you lots of session related headaches. The article at http://msdn.microsoft.com/en-us/library/ms178586.aspx will give you a good overview on how to accomplish this.

Answer 3

Greetings David,

This kind of problems is difficult to be solved by asking online, they need to be examined on-site, so I won't give you an answer, but just some hints:

• Does this application use authentication and authorization? if so, the authentication cookie may be expiring after leaving the app inactive for a long time, and if you click the "select" button you're redirected to the login page, but the login page itself may be having a problem that causes a redirection loop to occur, which causes most browsers to display the "This page cannot be displayed" message after a couple of runs of the loop. The loop may be caused by other factors, so I suggest tracing your http interactivity using Fiddler, you will know what response the server gives, and why the browser displays the error page.
• With fiddler attached, I suggest running the app in debug mode, and from the visual studio menu, select Debug>Exceptions, then check all the boxes in the "Thrown" and "User unhandled" columns, this will cause the debugger to break on every exception even they're handled.
• The last point is irrelevant: I suggest changing the way in which users select from the grid. instead of a "select" link button, place a link with the url of the other page, and pass the id of the selected item as a url parameter. This will save a round trip to the server, and the tiny session storage overhead. In the other page, you must take care that someone won't play with the url parameter to manipulate data he doesn't have permissions to manipulate.

Answer 4

Try setting EnableViewStateMac to falseon the page to see if it is related to this.