Asp.Net FileUpload doesn't work on Ajax UpdatePanel

I have an ASP.Net FileUpload inside an UpdatePanel. When I click on a save button inside the same updatepanel and check on serverside if that control hasFile it is allways false.

Where is my error? Do I need to post the entire page?

Tha开发者_JAVA百科nk you!

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unfortunately due to javascript sandboxing you will need to post the entire page