# NHibernate Persistence Upgrade Version 6 to 7



## Accessing the ISession

The way the NHibernate's `ISession` object is accessed has changed. This object is no longer accessible through dependency injection or `NHibernateStorageContext`. When Property or Constructor injection is used to get an instance of `ISession` directly or through `NHibernateStorageContext`, the code needs to be refactored after the upgrade to this version.

```csharp
public class OrderHandler :
    IHandleMessages<OrderMessage>
{
    public Task Handle(OrderMessage message, IMessageHandlerContext context)
    {
        var nhibernateSession = context.SynchronizedStorageSession.Session();
        nhibernateSession.Save(new Order());
        return Task.CompletedTask;
    }
}
```

As shown in the above snippet, the only way to access the `ISession` object is through the `Session()` extension method on `IMessageHandlerContext.SynchronizedStorageSession`.

The reason for removing the registration from dependency injection was to expose internal components of NServiceBus as little as possible and to have fewer behavioral changes in future versions. As such, the extension method called `RegisterManagedSessionInTheContainer()` which used to enable this behavior is obsolete and can be removed.


## Customizing the ISession Creation

It is no longer possible to customize the `ISession` creation process. As such, the extension method call `UseCustomSessionCreationMethod()` is no longer needed and should be removed.

Since most of the methods available on the `ISessionFactory` are related to caching and with this [existing NHibernate bug](https://nhibernate.jira.com/browse/NH-3023) (see also [accessing data](/persistence/nhibernate/accessing-data.md)), the benefit of having a customizable `ISession` creation is debatable. To customize the created `ISession` object, for example to apply a filter on the session level, the code must be moved to the handler and applied to the `ISession` object on the Context.


## Unique attribute no longer needed

NServiceBus will automatically make the correlated saga property unique without the need for an explicit `[Unique]` attribute. This attribute can be safely removed from saga data types.

Refer to the [NServiceBus upgrade guide for migrating from Version 5 to 6](/nservicebus/upgrades/5to6/handlers-and-sagas.md) to learn more about changes regarding sagas.