Hi Godwin,
Trying to keep the file upload within the update panel and within the flow of filling out the form would only open a can of worms and introduce other problems to solve. I think simple solutions are best and most stable, having the file upload on a separate page after completing the rest of the form reduces problems, reduces the likelihood of certain types of errors, and makes it easier to enforce security correctly. Changing this is not something I plan to do at the moment.
Best,
Joe