Explicitly flushing NHibernate ISession at the end of every request

1-rego.cs

    class WebRegistrationModule : Module
    {
        protected override void Load(ContainerBuilder builder)
        {
            builder.RegisterControllers(ThisAssembly);
            builder.RegisterModule(new AutofacWebTypesModule());

            RegisterDatabaseComponents(builder);
        }

        private void RegisterDatabaseComponents(ContainerBuilder builder)
        {
            builder.Register(context => NhibernateConfig.CreateSessionFactory().OpenSession())
                .As<ISession>()
                .InstancePerRequest()
                .OnRelease(session =>
                    {
                        if (session.IsDirty())
                            session.Flush();        // deletes won't work without explicit .Flush()
                            
                        session.Dispose();
                    });
        }
    }

2-amvccontroller.cs

        [HttpPost]
        public ActionResult CreateIC(string code, string description)
        {
            _session.Save(new IntegratedCircuit { Code = code, Description = description });
            AddPageAlert("IC added successfully.", AlertType.Success);
            return RedirectToAction("Index");
        }

3-anapicontroller.cs

        public HttpResponseMessage Post(int id)
        {
            var ic = _session.Load<IntegratedCircuit>(id);
            _session.Delete(ic);
            return new HttpResponseMessage(HttpStatusCode.OK);
        }