Item refetched from unit of work, but query performed again anyway

I suspect this was already asked, but I can't find anything.

Using a single unit of work, I fetch an item by Id = 3.
uow.Items.Single(p => p.Id == 3);

I do something else. The record is changed in meantime in the database by someone else.

Than I fetch again from the same unit of work by Id = 3.
uow.Items.Single(p => p.Id == 3);

Now, I do get the proper "old" unchanged cached item from the unit of work, but what I am not sure about, is why is the second query sent to the database again.

The reason for the query going to the server again, is down to the behavior of the LINQ query.

You are probably expecting it to do something similar to uow.FindOne<Item>(3), where it would first lookup the key in the identity map and return the cached entity if it exists. This is finding by key.

However, it treats this type of query as a Find<Item> with the criteria of (Id == 3). As with any query which LightSpeed performs, when it fetches a result set and is loading entities (as opposed to a projected result) from the set, it will first load the Id from the current record and then see if it already has that entity in the cache - if it does it returns it, if not it will continue with loading the entity from the record. You will also see the same result if you use FindOne with a query as opposed to a key.

Hope that explains it :) If you want to avoid the extra database hit and are searching by key as you are in the example above I would suggest you try using FindOne :)

OK, cleared.

Thanks Jeremy.