How to obtain the mesh of a face of an object?

Rusko

I am trying to develop a surface path planning AddIn of a face. I found that MeshFace contains all (presumably) all the data I need such as vertices, normals and so on for complex surfaces. I have already the face selection working. Is there a possible way to cast it to MeshFace or getting the face by indexing?  

I've tried directly casting it or finding it by face id (i do not know if that will even work)