The last thing I will compare in this round of Battle of the ORM’s is how NHibernate and the Entity Framework handle persistence. So first of all I want to vent one of my pet peeves, which is the myth of persistence ignorence.

Persistence ignorence is a term used to describe a persistence mecanism that does not contaminate the domain model and hence the business logic. This means that the model can be ignorent of how it is stored and not contain detals about the datastore. I think this a very important design goal to strive for, however actually obtaining true ignorence is a myth and something no ORM is even close to achieving.

In the previous Battle of the ORM's post I looked at setting up and configuring NHibernate and Entity Framework. So the next step is to get down to business and look at querying - the most important part of an ORM.

Gimme gimme gimme

First I need to address that the Entity Framework CTP5 has been released. This means that some more features have been added, which you can read about on Scott Guthries blog. Besides that there are some classes that have been renamed, which actually makes my last post mildly obsolete already. The renaming means that the Database class now is called DbDatabase – apparently redundancy is the new black – and that the databaseinitializer classes are called CreateDatabaseIfNotExists, DropCreateDatabaseAlways and DropCreateDatabaseIfModelChanges.

These days most developers use LINQ, myself included, but a very common issue is that not all LINQ implementations are created equal. Actually the reason I started this whole comparison project, was because I have been using an NHibernate 2.x, where LINQ to NHibernate was a seperate project - and suffice to say I have had my share of fights with it. Now it has been "baked in", and it has taken a pretty big leap forward.

Following up on my last post and on reading NHibernate 3.0 Cookbook I decided to download the latest NHibernate bits (v. 3 CR1), and do a comparison to Microsofts Entity Framework.
NHibernate and Entity Framework are what most developers reguard as the top Object Relational Mappers out there. So looking at how they stack up is pretty important in order to be able to choose the right ORM for a given project.