C # Nhibernate Session Not Updated

Question

I notice strange behavior in my application that uses NHibernate

To give you a little background, there are two tables in the database:

1) Transaction 2) Car

The deal has a one-to-one connection with the vehicle.

I have a helper database class that has Save and GetAll methods.

Therefore, when I run the following code, everything works as intended.

Transaction t;

using (var session = sessionFactory.OpenSession())
{
    t = dbHelper.GetAll<Transaction>(session)[0];

    t.Vehicle.Odometer = "777";

    dbHelper.Save(t, session);  // This updates the vehicle table odometer property to 777    
}

However, if I change my code as follows

Transaction t;

using (var session = sessionFactory.OpenSession())
{
    t = dbHelper.GetAll<Transaction>(session)[0];
}

using (var session = sessionFactory.OpenSession())
{
    t.Vehicle.Odometer = "777";

    dbHelper.Save(t, session);  // This does not update the vehicle table.

    // but

    dbHelper.Save(t.Vehicle, session); // Works  
}

Does this mean that relationship properties are session dependent?

change

I use Fluent with AutoMapper, and this is one of the classes that I use:

internal class OneToOneConvention : IHasOneConvention 
{ 
   public void Apply(IOneToOneInstance instance) 
   { 
     instance.Cascade.All(); 
   } 
}

change

Here are two methods inside dbHelper

  public void Save<T>(T entity, ISession session) 
        {
            using (ITransaction transaction = session.BeginTransaction())
            {
                try
                {
                    session.SaveOrUpdate(entity);
                    transaction.Commit();
                }

                catch (Exception)
                {
                    transaction.Rollback();
                    throw;
                }
            }
        }

and getall

public IList<T> GetAll<T>(ISession session) where T : class
        {
                return session.CreateCriteria<T>().List<T>();
        }

Answer 1

. Transaction, NH Session. , using, . - , Session, Session . :

• Transaction
• CRUD ( NHibernate)
• Commit Rolback

Answer 2

--, . ?

, (dbHelper) NHibernate.