nHibernate Criteria for selecting all entities with empty child collections

Question

I'm having difficulty writing a Criteria to select all entities with empty child collections or empty grand-child collections. I can do these as separate Criteria but I'm having trouble combining into a single Criteria.

class structure:

public class Component
    {
        public IList<Version> Versions { get; set; }
    }

    public class Version
    {
        public IList<SubscribeEvent> SubscribedEvents { get; set; }
        public IList<PublishEvent> PublishedEvent { get; set; }
    }

This does not work:

return session
                .CreateCriteria<Component>("c")
                .CreateCriteria("Versions", "v")
                .Add(Restrictions.Or(Restrictions.IsEmpty("c.Versions"), Restrictions.And(Restrictions.IsEmpty("v.PublishedEvents"),
                                                                                        Restrictions.IsEmpty("v.SubscribedEvents"))))
                .SetCacheable(true);

Answer 1

I've managed to work out a solution, not sure if it is the best (I should buy NH profiler)

return session
            .CreateCriteria<Component>("c")
            .CreateAlias("Versions", "v", JoinType.LeftOuterJoin)
            .Add(Restrictions.Or(Restrictions.IsEmpty("c.Versions"),
                                 Restrictions.And(Restrictions.IsEmpty("v.SubscribedEvents"),
                                                  Restrictions.IsEmpty("v.PublishedEvents"))))
            .SetCacheable(true);