NHibernate in Key Update

Nhibermate rad dela key update. Shrani parent in child objekt, nato pa na childu naredi key update in ga nastavi na null. Rešitev:

[Set(0, Name = "CRDocumentPositionSet", Lazy = CollectionLazy.False)]
[Key(1, Column = "IdDocument", ForeignKey = "none", Update = false)]
[OneToMany(2, ClassType = typeof(CRDocumentPosition), NotFound = NotFoundMode.Ignore)]
private ISet _cRDocumentPositionSet;