This seemed to be the problem. I did not have stdafx.h declare at the begining of the source file, which refereneced MFC classes.
C1010: unexpected end of file while looking for precompiled header directive
If your project is an MFC AppWizard created project then this error results from not #including StdAfx.h as the first #include statement (before any other #includes, data declarations, or executable program code).
Thanks to all.