Ajax File Upload unusal behaviour when using sessions

I have just implemented an Ajax File Upload control that uses a progress bar. I am a little confused. When i use the control on pages that dont use sessions, the progress bar with no problems will show the user the actual progress of the file being uploaded from 0%,1%,2%,3%.......% to 100%. Now when i move this control onto a web page that uses a session, this session stores the user information such as screenname, email, etc... the file uploads with no problems but the problem is that the progress bar does allow the user to see the progress unti开发者_运维技巧l the file is finised uploading and the progress bar jumps straight from 0% to 100% uploaded and doenst really show the full progress of the file whilst being uploaded.

Why is this behaviour occuring when i use sessions? where the progress of the file being uploaded isn't being shown to the user until the file uploads.

i would be grateful for your feedback.

Thanks.

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The way to allow the progress bar to work is to use a httpmodule for the progress bar to update while the file is being processed serverside.