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.

A few weeks ago we got a copy of the NHibernate 3.0 Cookbook by Jason Dentler, which I was really looking forward to because of the scattered nature the existing documentation for NHibernate.

The word Cookbook really says a lot of how the book is structured, and how it should be used. The book consists of a bunch of recipes on how to cook with NHibernate – terrible wordplay, I know, and I am sorry :) So basically it can be a good idea with a quick readthrough, and then it will serve as a place to look up solutions to various scenarios you will be dealing with when using NHibernate.

If you are new to NHibernate you will of course also gain an overview of the different topics you need to know about and as an experienced user you might stumble upon some features you didn’t know about.

Actually I had not planned to go to JAOO this year, but first my good colleagues who run ANUG struck a good deal where Mads Torgersenand Oren Eini alias Ayende Rahienwould give a special talk in the evening for the usergroup. This was simply too good to pass up. After all, how often do you get the chance to see one of the Danes from the C# language team and Ayende – who is the guy behind tools like NHibernate and Rhino.Mocks.

On top of the “Geek night” as it was coined, I ended up going Wednesday for the .NET track as well. To my gain a colleague who already had a ticket could not go, so I was lucky enough to get the offer to go in his place.

It ended up being a very interesting night and day I think – with my only small complaint to Trifork, who did brilliantly, being that the .NET track was held in a building that was below par compared to “Musik huset” where the rest was held.

Key points for me was hearing Mads, Ayende twice and Udi Dahan. Madses talked about what it is like to work in the C# team, and the considerations they have to take. This was really interesting and its hard not to be a bit hit by national pride that there are actually two Danes on a team like that. 

Ayende mostly talked about his own projects with the talks focused around NH Prof and NHibernate. It is impressive to see him with a keyboard, even though I had hoped the focus of his talks would have been a bit wider. The one general issue he talked about was at the ANUG talk where he talked about concepts and features. On the upside in the day session we did get to see some of the stuff he has added to NHibernate where especially NHibernate Search looked quite interesting.

Udi Dahan gave my personal “talk of the day”, because I think he got the focus of the talk right, and managed to make it fun and interesting. The subject was pretty broad being “Scalability, Availability and Reliability”, but he made it pretty concrete without making it about a single product. The focus was on how a one way messaging architecture based around transactional queues could solve a lot of the typical issues that we run into as developers. Actually the fact that he has worked on NServiceBus did not come up until the talk was basically over and it was just named as a possible solution amongst a bunch of others.

NServiceBus will be the focus of the next ANUG meeting where my colleague Lasse Eskildsen will  be showing a bunch of good examples on how it can be used. So this was the perfect fuel to light up my interest for the subject. Besides what I have already written about there is one more topic that tickled my taste buds, which is Scala. It does not take much to get me going when it comes to programming languages, so maybe it is just me, but I think Ill have to take a look even though my focus right now is more on IronPython.