调用NHibernate ISession.get <T> （对象id）两次具有相同的id返回两个不同的实例

Question

It's my understanding -- eg from sources like First and Second Level caching in NHibernate -- that NHibernate's ISession.get<T>(object id) should, when using the "default" setup -- session, etc., return the same instance if called twice with the same id . However, I'm getting two separate instances.

I've seen vaguely-similar questions but no useful results with searches like this , and this .

Here's my get method:

BillingItem IEntityRepository.GetBillingItemByID(int id)
{
    var session = Helpers.NHibernateHelper.OpenSession();

    using (ITransaction tran = session.BeginTransaction())
    {
        var ret = session.Get<BillingItem>(id);
        tran.Commit();
        return ret;
    }
}

Here's my test, which is failing:

var repo = (IEntityRepository) new SqliteEntityRepository();
var bi1 = repo.GetBillingItemByID(26);
var bi2 = repo.GetBillingItemByID(26);
Assert.AreSame(bi1, bi2); // fails

Here's NHibernateHelper just in case you want to see it:

internal static class NHibernateHelper
{
    private static ISessionFactory _sessionFactory;

    internal static ISession OpenSession()
    {
        return SessionFactory.OpenSession();
    }

    private static ISessionFactory SessionFactory
    {
        get
        {
            if (_sessionFactory == null)
            {
                var configuration = new Configuration();
                configuration.Configure();
                configuration.AddAssembly(typeof(BillingItem).Assembly);
                configuration.AddAssembly(typeof(PaymentItem).Assembly);
                var mapper = new ModelMapper();
                mapper.AddMappings(typeof(Mappings.BillingItemMapping).Assembly.GetExportedTypes());
                mapper.AddMappings(typeof(Mappings.PaymentItemMapping).Assembly.GetExportedTypes());
                var mapping = mapper.CompileMappingForAllExplicitlyAddedEntities();
                configuration.AddDeserializedMapping(mapping, null);
                SchemaMetadataUpdater.QuoteTableAndColumns(configuration);
                _sessionFactory = configuration.BuildSessionFactory();
            }

            return _sessionFactory;
        }
    }
}

What am I missing here?

Answer 1

This must be true, because in a snippet above we are using ... almost anti-pattern ... a very short session:

using (ISession session = Helpers.NHibernateHelper.OpenSession())
{ ... }

That is not what we usually need. We need a Unit of Work session. In web app, it usually last through whole request... (In a desktop... there should be some UoW workaround) .

So, if there are two different sessions - then both produce different run-time instance.

Answer 2

Repositories should not be responsible for handling transactions. You need to have a single instance of unit of work that would allow you to run multiple queries in the same session/transaction.

It looks to me that the OpenSession() method creates a new session each time. Can you post the code for it?