I am working on a ASP.NET app and i have a need to post back to the server after a file is chosen in a FileUpload control without having to have the user explicitly click a \'su
The first answer had the right javascript, but ASP.NET does not necessarily expose the input control directly, so it is better to put the onchange event on the FileUpload control.
Another route to go is to provide rich uploading via flash/silverlight/ajax. A great component for this can be found at Ajax Uploader for about $100