Hey Marsel,

Thanks for you reply, I was already thinking of that as a work around, I'll try that! 

I seem to be stuck at a certain point. The main idea of the program is to select faces by their Material ID and then move them. 

So far I have this:

Dictionary<ushort, List> testDict = new Dictionary<ushort, List>();

TriObject triObj = (ITriObject)node.EvalWorldState(0, true).Obj.ConvertToType(0, m_Global.TriObjectClassID);

for (int index = 0; index < mesh.Faces.Count; index++)
{
       var face = mesh.Faces[index];
       ushort matId = face.MatID;

       if (testDict.ContainsKey(matId))
              testDict[matId].Add(index);
       else
              testDict.Add(matId, new List(){index});
}

I thought with this I would be saving the FaceID together with the MatID as key. So I'd be able to get a list of faceID's according to certain Key values (matID). However the index I'm saving is not the face index and I have no idea how to get it either. So now I'm wondering if anyone could help me finding the correct FaceID (the one you see when you select the face in Max or in the listener: $.EditablePoly.SetSelection #Face #{2} <-- "2"). 

Or am I wrong trying to get the same ID as maxscript and should I just use index to select my faces, but I also have no idea how... 

**EDIT:
I should've done some more research before posting this. I found out by checking mesh.FaceSel that the face index is correct afterall. Now I just need to find out how to set a selection based of a BitArray. 

Any help would be appreciated!