SemiTransparent DynamicSelection with Halo with derived class

SemiTransparent DynamicSelection is a great feature for selection. But I have an issue to use it.

I derived a class named WorkingFace from Mesh. I followed the instruction from the article https://devdept.zendesk.com/hc/en-us/articles/5827291631250-Semi-transparent-Selection-with-Halo-  and everything work fine.

But I want select only faces in WorkingFace entity only, but the SelectionFilterMode property can only filter the selecton by type like edge, face etc. How can I achieve this function?