NHibernate QueryOver how to join on non declared relationship

Question

How to do the following join to return Users who have access to a Company given a company id. The problem is there is no explicit relationship using a User object between Us

Answer 1

As of 5.1.0, it is possible to make hibernate generate an actual sql join on an undeclared (unmapped) relationship. E.g. all orders sorted by customer's spending:

var criteria = _session
    .CreateCriteria("order");

criteria
    .CreateEntityAlias(
        "customer",
        Restrictions.EqProperty("order.customerId", "customer._id"),
        JoinType.LeftOuterJoin,
        typeof(Customer).FullName)
    .AddOrder(new Order("customer._lifetimeSpending", ascending:false));

return criteria.List();

Also possible with QueryOver (sample from NHibernate docs):

Cat cat = null;
Cat joinedCat = null;

var uniquelyNamedCats = sess.QueryOver(() => cat)
    .JoinEntityAlias(
        () => joinedCat,
        () => cat.Name == joinedCat.Name && cat.Id != joinedCat.Id,
        JoinType.LeftOuterJoin)
    .Where(() => joinedCat.Id == null)
    .List();