Hello everyone!
I'm currently developing a web application (using one session per view), roughly separated in 3 tiers: data access, business and UI. The process tier is session agnostic.

The problem is, I intended to keep a reference to the data objects (fetched by NHibernate) at UI level, in order to reuse them in the following sessions (for instance, when logging in a user I think I could fetch the user info only the first time and then keep it, or when reading an article I could fetch the article's data and the reuse it in case the user wants to comment or tag it). Is this approach fundamentally flawed?

But anyway, the real question is that when I'm reusing some detached object in the business tier I need a way to reattach it to the current session. Currently I simply call SaveOrUpdate on each object the business tier reuses, but I fear this might be inefficient when calling it multiple times on objects that are already attached (because they were fetched in the current session: but the business layer has no way to know it).
I'm looking for a way to find out if an object is attached to a particular session or not: I tried to use NHibernateProxyHelper in order to get the objects lazy initializer and then compare the sessions, but this doesn't work (it seems the objects I fetch through NHibernate are not proxied). Isn't there a "IsAttached(object o)"-like method somewhere?

Thank you very much. :)

To find out if an entity is already attached to a particular session, use

In order to attach an object to a session I'd recommend to look at
- refresh (load the current state from the database in the current object)
- get / load (loads the current state from session or if necessary from the database)

- using update or merge is possible but probably not what you want, because it causes updates and/or exceptions, when the object is changed in the meantime

In order to prevent excessive database roundtrips configure a 2nd level cache with short timeout times (1minute!?) so that repeatet accesses to the same object via get or load get satisfied by the cache

HTH
Jens

Thanks a lot, exactly what I was looking for. Works like a charm! :)



Yes, I will definitely give a look to 2nd level caching. Do you know if the Refresh call always results in a database roundtrip or will it eventually check the cache too?
Thank you.