NHibernate:使用Fluent Nhibernate来保存子对象

public class ParentMap : ClassMap<Parent>
{
    public ParentMap()
    {
        Id(x => x.Id);
        Map(x => x.Name);
        HasMany(x => x.Children)
            .KeyColumn("ParentId")
            .Cascade.AllDeleteOrphan();
    }
}

public class ChildMap : ClassMap<Child>
{
    public ChildMap()
    {
        Id(x => x.Id);
        Map(x => x.Name);
        References(x => x.Parent);
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        var sessionFactory = Fluently.Configure()
            .Database(MsSqlConfiguration.MsSql2012.ConnectionString("..."))
            .Mappings(m => m.FluentMappings.AddFromAssemblyOf<ParentMap>())
            .BuildSessionFactory();

        using (var session = sessionFactory.OpenSession())
        {
            using (var transaction = session.BeginTransaction())
            {
                var parent = new Parent { Name = "Parent 1" };
                parent.Children.Add(new Child { Name = "Child 1" });
                parent.Children.Add(new Child { Name = "Child 2" });

                session.Save(parent);

                transaction.Commit();
            }
        }
    }
}