title: ASP.Net file upload with an empty posted files collection
body: <p>I have an ASP.NET file upload control which sits as part of a form. The file upload control is on the content page while the form definition is on a master page across the site. I've added multipart/form-enc to the form on the master page.</p>
  
  <p>I'm using jQuery to submit the form as I show a dialog box from jQuery UI.</p>
  
  <p>When I post, no file is returned to the server. The file upload control has no file and HttpFileCollection is empty. How can I find the posted file?</p>