According to Microsoft the FileUpload control is not compatible with an AJAX UpdatePanel.
I am aware that a PostBackTrigger can be added to the submit button of the form like this:
<Triggers> <asp:PostBackTrigger ControlID="Button1" /> </Triggers>
The problem is that this forces the form to perform a full post-back which voids out the whole point of using the UpdatePanel in the first place. Is there a workaround to this issue that does not cause the whole page to refresh?