I mentioned ItemTypeLibraryMgr in a post on the Forum.  It's a helper class to wrap common usage of the MicroStationAPI with Item Type libraries. Use at your own risk.  Support is not included.

You need these headers...

#include <Mstn/MdlApi/MdlApi.h>
#include <Mstn/MicroStation.r.h>
#include <DgnPlatform/DgnPlatform.r.h>
#include <ECObjects/ECObjects.h>

Here's the class declaration...