Hello, I have a question about Transaction.

I need to insert relationated objects.
I have 3 tables and 3 objects mapped.
I have the following case:
....
session = _sessionFactory.OpenSession();
transaction = session.BeginTransaction();

session.save(objeto1);
objeto2.propertyx=administrationobject1.find(id);
session.save(objeto2);
session.save(objeto3);
transaction.Commit();
}
catch
{
if(transaction != null)
transaction.Rollback();
throw;
}
finally
{
if(session != null)
session.Close();
}
If I use a Transaction, i have a problem in this administrationobject1.find(id), because these method use a a new session, and session time expired conection in this method.
Any idea?