public class Source
    {
        public virtual int ID { get; set; }
        public virtual string Name { get; set; }

        private IList<Comment> _comments;
        public virtual IList<Comment> Comments
        {
            get { return new List<Comment>(_comments).AsReadOnly(); }
            private set { _comments = value; }
        }

        public virtual Comment LastComment {get; private set;}

        public Source()
        {
            Comments = new List<Comment>();
        }

        public virtual void AddComment(Comment comment)
        {
            LastComment = comment;
            comment.Source = this;
            _comments.Add(comment);
        }
    }

    public class Comment
    {
        public virtual int ID { get; set; }
        public virtual DateTime Date { get; set; }
        public virtual string Comments { get; set; }
        public virtual Source Source { get; set; }

    }

    public class SourceMap : ClassMap<Source>
    {
        public SourceMap()
        {
            Table("Source");
            

            Id(x => x.ID);
            Map(x => x.Name).Column("SourceName");
            HasMany(x => x.Comments).Access.CamelCaseField(Prefix.Underscore).Inverse().Cascade.All();
            References(source => source.LastComment).Fetch.Join();
        }
    }

    public class CommentMap : ClassMap<Comment>
    {
        public CommentMap()
        {
            Id(x => x.ID);
            Map(x => x.Date);
            Map(x => x.Comments);
            References(x => x.Source).Column("SourceID");
        }
    }

    [TestFixture]
    public class EagerFetchingFixture
    {
        #region Setup/Teardown

        [SetUp]
        public void SetUp()
        {

            var persister = SQLiteConfiguration
                .Standard
                .UsingFile("Test.db")
                .ShowSql();


             _config = Fluently
                 .Configure()
                 .Database(persister)
                 .Mappings(map => map.FluentMappings.AddFromAssemblyOf<Source>())
                .BuildConfiguration();

             _sessionFactory = _config.BuildSessionFactory();

             new SchemaExport(_config).Execute(true, true, false);
        }

        #endregion

        private ISessionFactory _sessionFactory;
        private Configuration _config;

        [Test]
        public void Test()
        {
            using(var session = _sessionFactory.OpenSession())
            {
                var source = new Source {Name = Guid.NewGuid().ToString()};

                source.AddComment(new Comment {Comments = Guid.NewGuid().ToString(), Date = DateTime.Now});
                source.AddComment(new Comment { Comments = Guid.NewGuid().ToString(), Date = DateTime.Now});
                source.AddComment(new Comment { Comments = Guid.NewGuid().ToString(), Date = DateTime.Now});

                session.Persist(source);
                session.Flush();
                session.Clear();

                var s2 = session.Get<Source>(1);

                var comment = s2.LastComment.Comments;
                
            }
        }

drop table if exists "Comment"

    drop table if exists Source

    create table "Comment" (
        ID  integer,
       Date DATETIME,
       Comments TEXT,
       SourceID INTEGER,
       primary key (ID)
    )

    create table Source (
        ID  integer,
       SourceName TEXT,
       LastComment_id INTEGER,
       primary key (ID)
    )
NHibernate: INSERT INTO Source (SourceName, LastComment_id) VALUES (@p0, @p1); select last_insert_rowid();@p0 = 'cfe8d711-876c-4bca-96f1-f2f410d8fdea', @p1 = NULL
NHibernate: INSERT INTO "Comment" (Date, Comments, SourceID) VALUES (@p0, @p1, @p2); select last_insert_rowid();@p0 = 03.11.2010 16:07:20, @p1 = '44c7b1fc-8bae-4cb3-a4ac-5dcdbb02884a', @p2 = 1
NHibernate: INSERT INTO "Comment" (Date, Comments, SourceID) VALUES (@p0, @p1, @p2); select last_insert_rowid();@p0 = 03.11.2010 16:07:20, @p1 = '01156992-8cab-4100-8311-0e9e29e9c659', @p2 = 1
NHibernate: INSERT INTO "Comment" (Date, Comments, SourceID) VALUES (@p0, @p1, @p2); select last_insert_rowid();@p0 = 03.11.2010 16:07:20, @p1 = 'af72a15a-0aa5-4ca5-ab97-40b8e0e53d86', @p2 = 1
NHibernate: UPDATE Source SET SourceName = @p0, LastComment_id = @p1 WHERE ID = @p2;@p0 = 'cfe8d711-876c-4bca-96f1-f2f410d8fdea', @p1 = 3, @p2 = 1
NHibernate: SELECT source0_.ID as ID1_1_, source0_.SourceName as SourceName1_1_, source0_.LastComment_id as LastComm3_1_1_, comment1_.ID as ID0_0_, comment1_.Date as Date0_0_, comment1_.Comments as Comments0_0_, comment1_.SourceID as SourceID0_0_ FROM Source source0_ left outer join "Comment" comment1_ on source0_.LastComment_id=comment1_.ID WHERE source0_.ID=@p0;@p0 = 1