Accessing SessionState in Application_Err or

[Nemisis]

Hi everyone,

I am trying to create a custom error page, that the user gets shown
when a error has occurred within my website. The code works
perfectly, apart from when an invalid URL is typed in, then i am
unable to pass the exception from the global.asax file to the page via
the sessionstate. Everytime i try to pass something into the
sessionstate i get a error message of 'Object reference not set to an
instance of an object.'

Does anyone know how to get around this error? My code is below

GLOBAL.ASAX PAGE CODE

Sub Application_Err or(ByVal sender As Object, ByVal e As
EventArgs)
' Fires when an error occurs

Dim ctx As HttpContext = HttpContext.Cur rent
Dim LastException As Exception = ctx.Server.GetL astError
Dim Exception As New ExceptionItem(L astException)

' clear the error
ctx.Server.Clea rError()

HttpContext.Cur rent.Session("H ELLO") = "AAA"
HttpContext.Cur rent.Session.Ad d("LastExceptio n", Exception)

Me.Response.Red irect("~/Errors/GeneralError.as px")
End Sub
CUSTOM ERROR PAGE CODE

Protected Sub Page_Load(ByVal sender As Object, ByVal e As
System.EventArg s) Handles Me.Load

Dim Master As eContrack = Page.Master

Master.SectionT itle = "An error has occurred"

' Session("LastEx ception") is created in the Error event
of global.asax
Dim Exception As ExceptionItem =
CType(Session(" LastException") , ExceptionItem)

Exception.Inser t()

' See if errors should be sent by email
If
ConfigurationMa nager.AppSettin gs("SendErrorBy Email").ToStrin g = "true"
Then
Exception.Email (ConfigurationM anager.AppSetti ngs("SendErrorT oEmail"),
HelperMethod.Ge tDns)

End If

End Sub

Thanks in advance

[Mike Hofer]

On Mar 12, 1:07 pm, "Nemisis" <darrens2...@ho tmail.comwrote:

Hi everyone,

I am trying to create a custom error page, that the user gets shown
when a error has occurred within my website. The code works
perfectly, apart from when an invalid URL is typed in, then i am
unable to pass the exception from the global.asax file to the page via
the sessionstate. Everytime i try to pass something into the
sessionstate i get a error message of 'Object reference not set to an
instance of an object.'

Does anyone know how to get around this error? My code is below

GLOBAL.ASAX PAGE CODE

Sub Application_Err or(ByVal sender As Object, ByVal e As
EventArgs)
' Fires when an error occurs

Dim ctx As HttpContext = HttpContext.Cur rent
Dim LastException As Exception = ctx.Server.GetL astError
Dim Exception As New ExceptionItem(L astException)

' clear the error
ctx.Server.Clea rError()

HttpContext.Cur rent.Session("H ELLO") = "AAA"
HttpContext.Cur rent.Session.Ad d("LastExceptio n", Exception)

Me.Response.Red irect("~/Errors/GeneralError.as px")
End Sub

CUSTOM ERROR PAGE CODE

Protected Sub Page_Load(ByVal sender As Object, ByVal e As
System.EventArg s) Handles Me.Load

Dim Master As eContrack = Page.Master

Master.SectionT itle = "An error has occurred"

' Session("LastEx ception") is created in the Error event
of global.asax
Dim Exception As ExceptionItem =
CType(Session(" LastException") , ExceptionItem)

Exception.Inser t()

' See if errors should be sent by email
If
ConfigurationMa nager.AppSettin gs("SendErrorBy Email").ToStrin g = "true"
Then

Exception.Email (ConfigurationM anager.AppSetti ngs("SendErrorT oEmail"),
HelperMethod.Ge tDns)

End If

End Sub

Thanks in advance

Please forgive me for being thickheaded; I get like that sometimes.
You're describing a NullReferenceEx ception. I'm not certain if it's
happening in global.asax or if it's happening in your custom error
page. I *think* it's happening in the custom error page.

If it's happening in the custom error page, its meaning will depend on
the line that the exception is occurring on. If it's happening on the
line where you're retreiving data from the session, I'd surmise that
it means that you either (a) don't have a session or (b) have a new
session and the value you're asking for isn't there.

However, I don't know what line the exception is being thrown from.
Could you be a little more specific?

Thanks!

[Nemisis]

Please forgive me for being thickheaded; I get like that sometimes.

You're describing a NullReferenceEx ception. I'm not certain if it's
happening in global.asax or if it's happening in your custom error
page. I *think* it's happening in the custom error page.

If it's happening in the custom error page, its meaning will depend on
the line that the exception is occurring on. If it's happening on the
line where you're retreiving data from the session, I'd surmise that
it means that you either (a) don't have a session or (b) have a new
session and the value you're asking for isn't there.

However, I don't know what line the exception is being thrown from.
Could you be a little more specific?

Sorry, i forgot to say where the error is occurring, Duh. lol.

The error is occurring when i try and set a session variable in the
global.asax file. The exact line where the error occurs is.

HttpContext.Cur rent.Session.Ad d("LastExceptio n", Exception)

I have even tried writing it like

HttpContext.Cur rent.Session("L astException") = Exception
but that still doesnt work. I have checked that Exception actually
does have values set, and it does. And to even test it further, i
wrote in the following line of code to test setting a session
variable, and it still comes up with the same error.

HttpContext.Cur rent.Session("H ELLO") = "AAA"

I would really appreicate any help and insight as to why this is
happening. Thanks again

[Nemisis]

Sorry i forgot to write what line is causing the error Duh! :)

It is on the global.asax file when i am trying to set the value of a
session variable. The line is :

HttpContext.Cur rent.Session.Ad d("LastExceptio n", Exception)

I have even tried to change it so it reads

HttpContext.Cur rent.Session("L astException") = Exception

but that still doesnt work. I do no that there is a value in
Exception, so i am not trying to store a null object. I even tried
the following line, and i am still getting the error.

HttpContext.Cur rent.Session("H ELLO") = "AAA"

I would really appreciate any insight to this problem. Cheers

[Nemisis]

Sorry i forgot to write what line is causing the error Duh! :)

It is on the global.asax file when i am trying to set the value of a
session variable. The line is :

HttpContext.Cur rent.Session.Ad d("LastExceptio n", Exception)

I have even tried to change it so it reads

HttpContext.Cur rent.Session("L astException") = Exception

but that still doesnt work. I do no that there is a value in
Exception, so i am not trying to store a null object. I even tried
the following line, and i am still getting the error.

HttpContext.Cur rent.Session("H ELLO") = "AAA"

I would really appreciate any insight to this problem. Cheers

[John Saunders]

"Nemisis" <da*********@ho tmail.comwrote in message
news:11******** **************@ 30g2000cwc.goog legroups.com...

>Please forgive me for being thickheaded; I get like that sometimes.
You're describing a NullReferenceEx ception. I'm not certain if it's
happening in global.asax or if it's happening in your custom error
page. I *think* it's happening in the custom error page.

If it's happening in the custom error page, its meaning will depend on
the line that the exception is occurring on. If it's happening on the
line where you're retreiving data from the session, I'd surmise that
it means that you either (a) don't have a session or (b) have a new
session and the value you're asking for isn't there.

However, I don't know what line the exception is being thrown from.
Could you be a little more specific?

Sorry, i forgot to say where the error is occurring, Duh. lol.

The error is occurring when i try and set a session variable in the
global.asax file. The exact line where the error occurs is.

HttpContext.Cur rent.Session.Ad d("LastExceptio n", Exception)

I bet that HttpContext.Cur rent.Session is Nothing, or else
HttpContext.Cur rent is Nothing. Check to see which.

John

[Mike Hofer]

On Mar 13, 5:13 am, "Nemisis" <darrens2...@ho tmail.comwrote:

Please forgive me for being thickheaded; I get like that sometimes.
You're describing a NullReferenceEx ception. I'm not certain if it's
happening in global.asax or if it's happening in your custom error
page. I *think* it's happening in the custom error page.

If it's happening in the custom error page, its meaning will depend on
the line that the exception is occurring on. If it's happening on the
line where you're retreiving data from the session, I'd surmise that
it means that you either (a) don't have a session or (b) have a new
session and the value you're asking for isn't there.

However, I don't know what line the exception is being thrown from.
Could you be a little more specific?

Sorry, i forgot to say where the error is occurring, Duh. lol.

The error is occurring when i try and set a session variable in the
global.asax file. The exact line where the error occurs is.

HttpContext.Cur rent.Session.Ad d("LastExceptio n", Exception)

I have even tried writing it like

HttpContext.Cur rent.Session("L astException") = Exception

but that still doesnt work. I have checked that Exception actually
does have values set, and it does. And to even test it further, i
wrote in the following line of code to test setting a session
variable, and it still comes up with the same error.

HttpContext.Cur rent.Session("H ELLO") = "AAA"

I would really appreicate any help and insight as to why this is
happening. Thanks again

If the error is occurring there, then the problem is that you don't
have a valid session object. This is born out by the fact that you've
tried twice to write two different variables to the session, and both
of them raise the same exception.

So the next question I have for you is this: What is the exception
that is putting you in this exception handler in the first place?
Whatever it is, it's apparently occurring before you have a valid
session, or it's disconnecting the user from their session. I'd look
there.

Without a valid session, you won't be able to cache the exception
information in it. To prevent the NullReferenceEx ception, wrap the
offending statement in a conditional, as follows (assuming VB.NET):

If Not HttpContext.Cur rent.Session Is Nothing Then
HttpContext.Cur rent.Session.Ad d("LastExceptio n", Exception)
End If

Hope this helps!

Mike

[Nemisis]

If the error is occurring there, then the problem is that you don't

have a valid session object. This is born out by the fact that you've
tried twice to write two different variables to the session, and both
of them raise the same exception.

So the next question I have for you is this: What is the exception
that is putting you in this exception handler in the first place?
Whatever it is, it's apparently occurring before you have a valid
session, or it's disconnecting the user from their session. I'd look
there.

Without a valid session, you won't be able to cache the exception
information in it. To prevent the NullReferenceEx ception, wrap the
offending statement in a conditional, as follows (assuming VB.NET):

If Not HttpContext.Cur rent.Session Is Nothing Then
HttpContext.Cur rent.Session.Ad d("LastExceptio n", Exception)
End If

Hope this helps!

Mike

In order to get this error, i am trying to navigate to a page that
doesnt exist on my site ie. Home4.aspx. This causes the
application_Err or sub to be called, but the session is empty/null. If
i create a standard page, and write Throw New Exception(), again, the
application_err or code is called, but the session IS VALID, and i do
not get a NullReferenceEx ception.

Why do you get a nullreferenceex ception on a 404 error? Is it because
the page is not apart of your application, thus the session wont exist?

[Mike Hofer]

On Mar 13, 11:10 am, "Nemisis" <darrens2...@ho tmail.comwrote:

If the error is occurring there, then the problem is that you don't
have a valid session object. This is born out by the fact that you've
tried twice to write two different variables to the session, and both
of them raise the same exception.

So the next question I have for you is this: What is the exception
that is putting you in this exception handler in the first place?
Whatever it is, it's apparently occurring before you have a valid
session, or it's disconnecting the user from their session. I'd look
there.

Without a valid session, you won't be able to cache the exception
information in it. To prevent the NullReferenceEx ception, wrap the
offending statement in a conditional, as follows (assuming VB.NET):

If Not HttpContext.Cur rent.Session Is Nothing Then
HttpContext.Cur rent.Session.Ad d("LastExceptio n", Exception)
End If

Hope this helps!

Mike

In order to get this error, i am trying to navigate to a page that
doesnt exist on my site ie. Home4.aspx. This causes the
application_Err or sub to be called, but the session is empty/null. If
i create a standard page, and write Throw New Exception(), again, the
application_err or code is called, but the session IS VALID, and i do
not get a NullReferenceEx ception.

Why do you get a nullreferenceex ception on a 404 error? Is it because
the page is not apart of your application, thus the session wont exist?- Hide quoted text -

- Show quoted text -

Without seeing your code, I couldn't specifically answer your
question. :(

A 404 is generated for a number of reasons, however, and not always
because a page couldn't be found. (Microsoft might like you to believe
that a 404 is *always* raised for that reason, but you shouldn't just
take their word for it.)

First off, you know that the exception is occurring. I'd start by
addressing the exception. It sounds like you're trying to treat the
symptom (the fact that you don't have a session variable in your error
handler) instead of dealing with its cause (the fact that you're on
the error page to begin with).

Why are you even *on* this error page? How did you get here? What is
the condition that got you here? That's the defect that needs to be
resolved. Wrap that code in an exception handler. Don't rely on
global.asax to handle your exceptions. It's a FAILSAFE, not your main
exception handler.

Check this article out: http://aspnetresources.com/articles/...rrorPages.aspx

I'm not sure how familiar you are with this stuff, but it might shed
some light on the best practices for exception handling in ASP.NET.

Again, I hope I'm helping and not just confusing the snot out of ya.

Mike

[Nemisis]

Mike,

1. My code is at the top of the forum, u must of missed it.
2. I think i have not explained myself correctly, or you are not
getting what i mean. I can handle exceptions, that it fine, but i
just want to know why i cant get access to session variables when i am
in the application_err or sub, when i cause an error by directing to an
invalid/non existant page?
3. That is one of the articles i have read, it is a good article, and
as you can see my code is very similar