How to detect the signature of a file


I got source code (using winverifytrust API ) which detects whether
the given file is signed or not.
source code link :

I created an exe with that code and tested I faced one issue
when I pass the "C:\Windows\System32\ieframe.dll" it is showing that
this file is not signed.
If I check the same file using "sigverif" ieframe.dll is signed.

Please can any tell me what might be the reason for the above.

I am trying to implement the SIgnedCode class in VC++ (MFC or Win32) I
did not get any information on this in the web.

Please can any suggest me how to proceed.