Hibernate – NHibernate – Updating a table with a trigger on it causes an error – Unexpected row count: 2; expected: 1

I had this exact problem with fluent nhibernate. There appears to be a small bug in mapping one-to-many relationships and the relationships not automatically saving or cascading. See here for a posting about it on the Fluent NHibernate group.

Apparently, there is someone working on the issue!

I can;t say for sure that this is the issue with your code but it looks very similar to a problem I had. Hope that helps some!

Both Save and Delete must happen in a transaction and the transaction must be committed at the end.

like so:

public void Save(IEnumerable<T> toSave)
{
    using (ISession session = SessionFactory.OpenSession())
    {
        ITransaction transaction = Session.BeginTransaction();

        foreach (T item in toSave)
        {
            session.SaveOrUpdate(item);
        }

        transaction.Commit();           
        session.Flush();
    }
}

please note: you'll want to wrap that in a using and properly rollback... also, placement of where you're opening and committing the transaction will matter based on your scenario. You should also close the transaction when you're done...

Also, can you elaborate on where the exception is happening? It sounds like you're saving a parent and then the child is throwing because the parent's id is null? Or, is it actually throwing on saving the parent?