DomainModelEntityManager.SaveChanges(IEnumberable entities) only be
able to save the added entities and modified entities, but it can't
save the deleted entities, but DomainModelEntityManager.SaveChanges()
be able to save properly. But we do need
DomainModelEntityManager.SaveChanges(IEnumberable entities), because it
can save a specific GUI's data.
this is the delete method i'm using, it's able to delete the entities in cache
this is the save method, it works for add and modify, but doesn't work for delete.
the SaveIndividual might be a bit confusing you i think, acutually it just uses the SaveChanges(IEnumberable entities) method.