FileUpload Doesn't Work When Nested In UpdatePanel? C#

Answer 1

File Upload will not work with a partial post back. So just add this line at your page load

ScriptManager.GetCurrent(this).RegisterPostBackControl(this.YourControlID);

Or use PostBackTrigger.

Or You need special AsyncFileUpload control as defined in AjaxControl Toolkit.

You can check here.