Hi,
HTML @Page directive:
Check This:
1. CodeFile="ucSupportingDocuments.ascx.cs"
2. Inherits="UserControls_ucSupportingDocuments"
There could be two possible reasons:
1. First check for the CodeFile whether it is pointing to same code file or not.
2. Check for the class name, whether it is matching with the inherit attribute or not. The Inherits attribute should be same as your partial class name.
--Amit