session variable getting lost

[SAL]

Okay, don't bash me to hard for my design on this app, it's my first web app
and it's in production.
My basic design is using Datatables created via the designer with a business
logic class in between the datatable and ObjectDataSources.
In one page I had a Gridview with select enabled. When an row in the grid is
selected, I retrieve the SelectedValue, store the value in a Session
variable and redirect the response to another web page, which, has an
ObjectDataSource on it and a DetailsView. The ObjectDataSource on this page
retrieves the value of the Session variable set from the first page. The
problem is that the Session variable is randomly losing its value.
So, the ObjectDataSource's Business object's SelectMethod accepts a value to
select records by. How do I know that the value is getting lost?
Because no rows are returned as:
dr = dtAdapter.Rows(0)

throws an exception IndexOutOfRange.

My question is, is there some reason that my session variable evaporates
randomly?

Thanks in advance

SAL

 

[Mark Rae [MVP]]

My question is, is there some reason that my session variable evaporates
randomly?

No. Session variables will be lost when the Session times out, or when they
are overwritten / removed - does either of these situations apply here...?

 

[SAL]

Mark, thanks for the reply.
I do not see either of these things applying here. This happened twice this
morning for no apparent reason and then it didn't happen. I have not changed
the time out so it should still be 20 minutes and I am not overwriting them
as far as I can see. I can not reproduce it on my machine.

S

 

[Guest]

Sal,
The only time a Session item would be lost under "normal circumstances"
(e.g. it hasn't timed out by itself due to no page requests) is that IIS is
recycling the application. Recycling can be because of IIS settings, because
something touched one or more of the files in the web folder "tree", or
because you've got buggy code that's causing unhandled exceptions.
In any of these cases, you can bet that your Application, Session and Cache
items will all go down the potty.
Peter
--
http://www.eggheadcafe.com
unBlog: http://petesbloggerama.blogspot.com
BlogMetaFinder: http://www.blogmetafinder.com

Mark, thanks for the reply.
I do not see either of these things applying here. This happened twice this
morning for no apparent reason and then it didn't happen. I have not changed
the time out so it should still be 20 minutes and I am not overwriting them
as far as I can see. I can not reproduce it on my machine.

S

 

[Walter Wang [MSFT]]

Hi SAL,

Based on my understanding, you're redirecting to the second page right
after setting the session variable, right? If this is the case, there's no
reason the session variable will be lost due to session timeout. Could you
please double check if the session variable is really lost or it's because
the query that uses the variable to retrieve records from database returns
empty result?

By the way, there's another way to pass variables between pages using
Context.Items and Server.Transfer:

#Famil Jones : Pass Variables Between ASP.NET Pages
http://www.dotnetjunkies.com/WebLog/familjones/archive/2004/04/08/11020.aspx


Regards,
Walter Wang ([email protected], remove 'online.')
Microsoft Online Community Support

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[SAL]

Hmmm, thank you for the replies all.
Would it be possible for Walter or someone else to comment on the load that
using the Server.Transfer pattern would place on the server? So, is there an
increased load on the server using this model as compared to using Session
variables?

Thanks
SAL

Mark, thanks for the reply.
I do not see either of these things applying here. This happened twice
this morning for no apparent reason and then it didn't happen. I have not
changed the time out so it should still be 20 minutes and I am not
overwriting them as far as I can see. I can not reproduce it on my
machine.

S

 

[SAL]

Okay, so let's say that all of the things you've listed below are not
happening. But, that a Response.Redirect may be. The documentation states
that Redirect calls End which raises a ThreadAbortException. I do not see
this exception however. I am wondering if this could be at the root of my
random problem here...

Thanks for your responses
S

Sal,
The only time a Session item would be lost under "normal circumstances"
(e.g. it hasn't timed out by itself due to no page requests) is that IIS
is
recycling the application. Recycling can be because of IIS settings,
because
something touched one or more of the files in the web folder "tree", or
because you've got buggy code that's causing unhandled exceptions.
In any of these cases, you can bet that your Application, Session and
Cache
items will all go down the potty.
Peter
--
http://www.eggheadcafe.com
unBlog: http://petesbloggerama.blogspot.com
BlogMetaFinder: http://www.blogmetafinder.com

 

[George Ter-Saakov]

Here are some guesses why session might be lost.

1. Host must be the same. Example http://www.mysite.com and
http://mysite.com might be 2 different sites. Thus browser does not pass
cookies from one to another. Thus session might be lost. If for example you
logged in into http://mysite.com/login.aspx and then got redirected to
http://www.mysite.com

2. Basically comes from #1. http://www.mysite.com and http://132.234.123.123
are 2 different sites even if www.mysite.com resolves to 132.234.123.123

3. Application is recycled.
To verify #3 add folowing code to Global.asax You need to replace last
line clsGlobal.SendEmail with your emailing code.
This will send an email to you with a reason everytime application was
shutdown. Thus you will know.....Unless of course someone pulls a power plug
from the server. Then no email will be sent

protected void Application_End(Object sender, EventArgs e)

{

HttpRuntime runtime =
(HttpRuntime)typeof(System.Web.HttpRuntime).InvokeMember("_theRuntime",

BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.GetField, null,
null, null);

if (runtime == null)

return;

string shutDownMessage =
(string)runtime.GetType().InvokeMember("_shutDownMessage",

BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.GetField,
null, runtime, null);

string shutDownStack =
(string)runtime.GetType().InvokeMember("_shutDownStack",

BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.GetField,
null, runtime, null);

//send email to me

clsGlobal.SendEmail(String.Format("\r\n\r\n_shutDownMessage={0}\r\n\r\n_shutDownStack={1}",

shutDownMessage,shutDownStack), "Application Shutdown",
(e-mail address removed), null, null);

}



George

 

[Walter Wang [MSFT]]

Hi SAL,

Regarding difference between Response.Redirect and Server.Transfer, I think
following page is useful for your reference. Each approach has its own pros
and cons.

#Response.Redirect vs Server.Transfer
http://haacked.com/archive/2004/10/06/responseredirectverseservertransfer.as
px

Back to the original issue about losing session after Redirect, I think
George's suggestion is quite helpful.


Regards,
Walter Wang ([email protected], remove 'online.')
Microsoft Online Community Support

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that others may learn and benefit from your issue.
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[SAL]

Thank you for your reply and the article link.
I am currently investigating George's suggestion as well

S

 

[SAL]

George, thanks for you suggestion. I have implemented the Application_End
routine in Global.aspx and the application is getting shut down with the
following information. If you can help it would be great:

HostingEnvironment caused shutdown

at System.Environment.GetStackTrace(Exception e, Boolean needFileInfo)
at System.Environment.get_StackTrace()
at System.Web.HttpRuntime.ShutdownAppDomain()
at System.Web.Hosting.HostingEnvironment.ShutdownThisAppDomainOnce()
at
System.Web.Hosting.HostingEnvironment.InitiateShutdownWorkItemCallback(Object
state)
at System.Threading._ThreadPoolWaitCallback.WaitCallback_Context(Object
state)
at System.Threading.ExecutionContext.Run(ExecutionContext
executionContext, ContextCallback callback, Object state)
at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback(Object
state)


S

 

[kpg*]

Thank you for your reply and the article link.
I am currently investigating George's suggestion as well

Please post back here if (and when) you find the culprit.

I have stopped using sesion variables altogether becuase of
similar issues on a client's server, but am very interested
in what you figure out.

Now my client may well be changing the web.config file
which will cause the application to restart, all the more
reason to not use session varialbes (in my case).

Instead I pass info encrypted in the query string, which
works just fine, the only session variable I use is to
relay error messages to tan error page - if that gets
lost, oh well.

kpg

 

[Walter Wang [MSFT]]

Hi SAL,

This looks like a normal shutdown, try to use following method to log the
cause and the time it occurs:

#Logging ASP.NET Application Shutdown Events - ScottGu's Blog
http://weblogs.asp.net/scottgu/archive/2005/12/14/433194.aspx


Regards,
Walter Wang ([email protected], remove 'online.')
Microsoft Online Community Support

==================================================
When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.
==================================================

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[Walter Wang [MSFT]]

Hi SAL,

How's the issue now?

Not directly related, but I think following information might be useful:

#Thomas Marquardt's Blog : ASP.NET File Change Notifications, exactly which
files and directories are monitored?
http://blogs.msdn.com/tmarq/archive/2007/11/02/asp-net-file-change-notificat
ions-exactly-which-files-and-directories-are-monitored.aspx


Regards,
Walter Wang ([email protected], remove 'online.')
Microsoft Online Community Support

==================================================
When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.
==================================================

This posting is provided "AS IS" with no warranties, and confers no rights.

 

[SAL]

Okay, I did that. Now I'm getting this in the event log:

The description for Event ID ( 0 ) in Source ( .NET Runtime ) cannot be
found. The local computer may not have the necessary registry information or
message DLL files to display messages from a remote computer. You may be
able to use the /AUXSOURCE= flag to retrieve this description; see Help and
Support for details. The following information is part of the event:

_shutDownMessage=HostingEnvironment caused shutdown

_shutDownStack= at System.Environment.GetStackTrace(Exception e, Boolean
needFileInfo)
at System.Environment.get_StackTrace()
at System.Web.HttpRuntime.ShutdownAppDomain()
at System.Web.Hosting.HostingEnvironment.ShutdownThisAppDomainOnce()
at
System.Web.Hosting.HostingEnvironment.InitiateShutdownWorkItemCallback(Object
state)
at System.Threading.

Which I really don't understand. Help?

S

 

[SAL]

Hi Walter. It's just as bad as ever and what I don't get is that, I'm not
changing anything when this stuff occurs that I'm aware of. All I'm doing is
redirecting to another page, changing DetailsView states to edit, cancelling
the edit, clicking another menu item and doing the same thing all over again
and it will restart which causes the ID of the item the viewer is using to
be lost in the session variable. And, since the ObjectDataSource is getting
records based on this ID, the app fails with a web page that isn't showing
any data.

S

 

[SAL]

kpg,
what I figured out was the app was getting recycled due to a limit I had set
on virtual memory. There are times when the virtual memory usage jumps up
dramatically and then it pops right back down. The app does not appear to be
leaking memory at this time. So, I unchecked that option in the App pool's
configuration.
I used information garnered from this link to aid me in my quest, although I
haven't completely implemented Peter's Exception Engine.
http://www.eggheadcafe.com/articles/20030816.asp

I placed this code in my Application_Error routine in my Global.asax file:

Sub Application_Error(ByVal sender As Object, ByVal e As EventArgs)
' Code that runs when an unhandled error occurs
' check to see if the ASPNETApplication log exists
Dim b As Boolean
Try
b =
Convert.ToBoolean(ConfigurationManager.AppSettings("logAppErrors"))
Catch ex As Exception

End Try
If Not b Then Exit Sub

If Not System.Diagnostics.EventLog. _
SourceExists("AnnexationTrackerApplication") Then
System.Diagnostics.EventLog. _
CreateEventSource("AnnexationTrackerApplication",
"Application")
End If
System.Diagnostics.EventLog. _
WriteEntry("AnnexationTrackerApplication",
Server.GetLastError().GetBaseException().Message)

End Sub

The message appeared in the system event log not the application event log.

HTH
S

 

[Carlos Vasquez]

There is a problem with losing values in Session Variable. I am
currently troubleshooting as to why. I am working with tabs and all
code is on the same page and my session variables are dropping.
Microsoft acknowledge this is a problem:
http://support.microsoft.com/kb/316148. I am still trying to figure out
why I am losing my session variables. None of the issues mentioned here
or on microsoft have been found to be the culprit.

If anyone knows why, I would like to know.

 

[Juan T. Llibre]

That KB is over 2 years old.

Antivirus scans are but one of the possible reasons for applications to restart,
which in turn causes the loss of session variables if session state is kept in-process.

Modifying the source code of your Web application will
cause ASP.NET to recompile source files into assemblies.

When you modify the top-level items in your application, all other assemblies
in the application that reference the top-level assemblies are recompiled as well.

In addition, modifying, adding, or deleting certain types of files
within the application's known folders will cause the application to restart.

The following actions will cause an application restart:

1. Adding, modifying, or deleting assemblies from the application's Bin folder.

2. Adding, modifying, or deleting localization resources
from the App_GlobalResources or App_LocalResources folders.

3. Adding, modifying, or deleting the application's Global.asax file.

4. Adding, modifying, or deleting source code files in the App_Code directory.

5. Adding, modifying, or deleting Profile configuration.

6. Adding, modifying, or deleting Web service references in the App_WebReferences directory.

7. Adding, modifying, or deleting the application's Web.config file.