Nhibernate documentation refers to CriteriaUtil whitch is removed from 2.1

http://nhforge.org/doc/nh/en/index.html#querycriteria-associations

In chapter 14.4. Associations:

Note that the kittens collections held by the Cat instances returned by the previous two queries are not pre-filtered by the criteria! If you wish to retrieve just the kittens that match the criteria, you must use SetResultTransformer(CriteriaUtil.AliasToEntityMap).

IList cats = sess.CreateCriteria(typeof(Cat))
.CreateCriteria("Kittens", "kt")
.Add( Expression.Eq("Name", "F%") )
.SetResultTransformer(CriteriaUtil.AliasToEntityMap)
.List();
foreach ( IDictionary map in cats )
{
Cat cat = (Cat) map[CriteriaUtil.RootAlias];
Cat kitten = (Cat) map["kt"];
}