How can i get the face persistent id?

I am working on dimxpert features. in one of the case , i need to know the dimxpert feature faces. I am getting the faces, but unable to get the face ids.

When i use below function to get the face persistent id, i am getting return value as a array of bytes. Here i am expecting face persistent id is a integer or long.

Can anybody faced similar problem, if yes please let me know.

object persistentFaceId = swModExt.GetPersistReference3(swFace2);

SolidworksApi/macros