Hello all,

I am using NH to load up ILists (Bags) with items.

I was hoping to make one call on a session to have everything load in a single database trip and then query the session object to return individual items (without making another db call).

I can't seem to get this to happen.

The code I'm using to load 'everything' is



I am then calling the following for individual items


Note - the Session object is the same and it hasn't been closed or disconnected.

If it helps, here is the map for clsItem...



Ideally, I guess that I would want to use a MAP/IDictionary to achieve this, however the collection has to participate in a bi-directional relationship, so (as I understand it) I'm restricted to bags and maps.

I'd be very appreciative if someone could give me some advice on how to tackle this issue. I've thought of putting a function in my collection wrapper that loops through the IList and returns a result... Or maybe even populate it into a Hashtable on construction... Are these the best ways to tackle this, or, Is there a way to return the object from the NH Session?

Thanks very much in advance,




Damien Sawyer

If I understood right, you wanted to preload with the CreateCriteria method and then retrieve the objects from cache on each Find call.

For NHibernate any query created with CreateCriteria, Find, CreateQuery, CreateSqlQuery transforms in a round-trip on the DB as it is no possibility for it to be sure that no new objects satisfying the search condition.

You can use Session.Get or Session.Load to obtain the object from the cache as both methods search in first level cache, the second level cache and the hit the db, but, these methods search by ID.

If the field you are searching by is the ID than you can use the Get or Load methods, otherwise you should find another approach on this, maybe caching by yourself the collection and than searching in it on the business layer.

If I understood right, you wanted to preload with the CreateCriteria method and then retrieve the objects from cache on each Find call.

For NHibernate any query created with CreateCriteria, Find, CreateQuery, CreateSqlQuery transforms in a round-trip on the DB as it is no possibility for it to be sure that no new objects satisfying the search condition.

You can use Session.Get or Session.Load to obtain the object from the cache as both methods search in first level cache, the second level cache and the hit the db, but, these methods search by ID.

If the field you are searching by is the ID than you can use the Get or Load methods, otherwise you should find another approach on this, maybe caching by yourself the collection and than searching in it on the business layer.

So use: Session.Get( typeof(clsItem), someLitmValue )

Good luck,
Dragos

Thanks Dragos,

That's a big help. I have to say, after a rough start, I'm finally starting to get the idea of NH. It really is fantastic! :-)


DS