I have a server code task which runs during a progress bar display (startTask). In the server side OnRunTask handler I save an object in session. Then in the ClientSideOnTaskDone client handler I update a callbackpanel (in a master page). In the Callbackpanel's OnExecute server handler, I try to get the object from the session but it's null?

What's the best way to pass an object in the workflow I described?

I saw a post about saving the session in a file as in: e.UpdateProgress(100, "../temp/" + session_file);
Is this the only way to pass the object? It seems I have to serialize the object in the file and then deserialize it upon reading. I prefer not to deal with files.

I am thinking of not using the runTask. i don't need to send updates to the progress bar. Just to close it when server code is done.