How to detect if a "ProjectItem" is a code file

Hi there,

Does anyone know how to detect if a file is a code file without relying on "ProjectItem.FileCodeModel" (in an add-in). I'm currently testing that for non-null but there seems to be a handle leak associated with it, as per my other post found here (still waiting for a response to that at this writing):

http://social.msdn.microsoft.com/Forums/vstudio/en-US/152ae36d-e004-4282-9ced-42a4c541501b/is-projectitemfilecodemodel-leaking-handles

Presumably I'd have to rely on the lower-level API, and I know how to get hold of a VSITEMID for instance, but can someone tell me what I need to call. Whatever the technique, it should only return true to indicate a code file if "ProjectItem.FileCodeModel" is also non-null. Thanks.