Session Variable-InvalidCastException

I use a Session variable to store a custom object (all properties contain
strings) between postbacks. On occasion, mostly when I change and save code,
when I refresh the web page to see the changes, I get an error:
"System.InvalidCastException was unhandled by user code -Unable to cast
object of type 'QueryParameters' to type 'QueryParameters'"
in the function below which is called during Page_Load (_queryParameters =
QueryParameters.getInstance())
Public Shared Function getInstance() As QueryParameters
Dim instance As QueryParameters
If IsNothing(Current.Session(SESSION_VARIABLE)) Then
instance = New QueryParameters()
instance.saveQPToSession()
Else
instance = Current.Session(SESSION_VARIABLE)
End If
Return instance
End Function
When I debug, a valid Session variable exists because the code goes to the
Else statement, and in the Watch window, I can see all the properties of the
custom object in the Session variable. Since 'instance' is typed as
QueryParameters and a Session variable exists that holds the object, I don't
understand why there is an error since these both seem to be typed correctly
as QueryParameters. Even when I explicitly type the session variable
(CType(Current.Session(SESSION_VARIABLE), QueryParameters)) the same error
appears.
If I close the browser completely, everything works, but I hate to have to
close a browser with every iteration of code changes.
Does anyone know why this error appears? Thanks for any help.Hi,
Don Miller wrote:
> I use a Session variable to store a custom object (all properties contain
> strings) between postbacks. On occasion, mostly when I change and save cod
e,
> when I refresh the web page to see the changes, I get an error:
> "System.InvalidCastException was unhandled by user code -Unable to cast
> object of type 'QueryParameters' to type 'QueryParameters'"
The symptoms make me think of that error:
http://weblogs.asp.net/scottgu/arch...ion-issues.aspx
Could that be it?
Greetings,
Laurent

> in the function below which is called during Page_Load (_queryParameters =
> QueryParameters.getInstance())
> Public Shared Function getInstance() As QueryParameters
> Dim instance As QueryParameters
> If IsNothing(Current.Session(SESSION_VARIABLE)) Then
> instance = New QueryParameters()
> instance.saveQPToSession()
> Else
> instance = Current.Session(SESSION_VARIABLE)
> End If
> Return instance
> End Function
> When I debug, a valid Session variable exists because the code goes to the
> Else statement, and in the Watch window, I can see all the properties of t
he
> custom object in the Session variable. Since 'instance' is typed as
> QueryParameters and a Session variable exists that holds the object, I don
't
> understand why there is an error since these both seem to be typed correct
ly
> as QueryParameters. Even when I explicitly type the session variable
> (CType(Current.Session(SESSION_VARIABLE), QueryParameters)) the same error
> appears.
> If I close the browser completely, everything works, but I hate to have to
> close a browser with every iteration of code changes.
> Does anyone know why this error appears? Thanks for any help.
>
Laurent Bugnion [MVP ASP.NET]
Software engineering, Blog: http://www.galasoft-LB.ch
PhotoAlbum: http://www.galasoft-LB.ch/pictures
Support children in Calcutta: http://www.calcutta-espoir.ch
>> "System.InvalidCastException was unhandled by user code -Unable to cast
> The symptoms make me think of that error:
> http://weblogs.asp.net/scottgu/arch...ion-issues.aspx
> Could that be it?
I tried the simple workaround (changing the web config file system "batch"
to false) and the error message persisted (run the application, type in
garbage in the code-behind, erase the garbage, save the file, hit refresh in
the browser). I am leary of applying the hotfix. I may just end up putting
my properties into hidden fields instead of an object in a Session variable
and forgetting this bug.
Something to do with changing the source code file and compilation.