public class Person
    {
        public virtual int ID { get; protected set; }
        public virtual string FirstName { get; set; }
        public virtual string LastName { get; set; }
        public virtual DateTime BirthDate { get; set; }
    }


    public class PersonMap : ClassMap<Person>
    {
        public PersonMap()
        {
            Table("PersonalInfo");
            Id(x => x.ID).GeneratedBy.Identity();
            Map(x => x.FirstName).Column("FirstName");
            Map(x => x.LastName).Column("LastName");
            Map(x => x.BirthDate).Column("BirthDate");
        }
    }


    [TestFixture]
    public class PersonFixture : FixtureBase
    {
        [Test]
        public void Save()
        {
            var person1 = new Person();
            var person2 = new Person();

            using (var session = _sessionFactory.OpenSession())
            {
                session.Save(person1);
                session.Save(person2);
                session.Flush();
            }

            Assert.That(person1.ID, Is.EqualTo(1));
            Assert.That(person2.ID, Is.EqualTo(2));
        }
    }