display custom entity

how to filter custom entity 
bellow code display list of all entity . 
i need to filter entity which are custom . 



                RetrieveAllEntitiesRequest req = new RetrieveAllEntitiesRequest();
                req.EntityFilters = EntityFilters.Privileges;
            
                req.RetrieveAsIfPublished = true;
                RetrieveAllEntitiesResponse resp = (RetrieveAllEntitiesResponse)service.Execute(req);