Several MVPs and other .NET Entity Framework testers (partly from the NHibernate camp) signed an open letter some weeks ago describing their concerns on some design decisions and the current state of what is about to become version 1.0 of the ADO.NET Entity Framework. Here is Microsoft's Tim Mallalieu's response.
Now I won't pretend to be an expert on Entity Framework (I spent two or three days playing around with it). I do have some Hibernate experience though (admitted, in the Java space). So this clearly qualifies me to throw in my 5 cents too, now doesn't it? ;-)
Here is what I think:
INORDINATE FOCUS THE DATA ASPECT OF ENTITIES LEADS TO DEGRADED ENTITY ARCHITECTURES
To be honest, my Hibernate POJOs never contained any logic code, they were plain data holders. This was a design decision that always worked fine for me, even if luminaries like Martin Fowler tend to criticize it. I think the requirement to combine data and logic code in entity objects, although comprehendible from an OOP perspective, is kind of overrated. Anyway one can still place that code in partial classes, what else can we ask for? What might be problematic in some application scenarios is that entity classes are linked to the whole Entity Framework by inheritance and code. They cannot exist "standalone" (e.g. in another tier without EF being around). One alternative are dynamic proxy classes being generated at runtime, but they have some drawbacks as well.
EXCESS CODE NEEDED TO DEAL WITH LACK OF LAZY LOADING
Once again, some people can't live without lazy loading. But lazy loading also might open a can of worms, e.g. in distributed environments like the ones I have to deal with. LazyInitializationException, anybody? I mostly prefer other loading strategies, like "Join Fetch". It boils down whether you (A) want to abstract the fact that there is a SQL database behind the hoods and only want to work on a cloud of objects or (B) the reason you use an ORM is to prevent tight coupling, database dependency and writing loads of mapping, routine SQL and infrastructure code (transaction management, etc) on your own, but still need to be in control of when and how data access actually happens. I am more of kind (B). EntityCollection.Load is just fine for me!
SHARED, CANONICAL MODEL CONTRADICTS SOFTWARE BEST PRACTICES
In this case the "best practice" depends on the type of application one is building. Nobody is being forced to have only "one model to rule them all" - one can as well apply the EF model within a single layer only.
LACK OF PERSISTENCE IGNORANCE CAUSES BUSINESS LOGIC TO BE HARDER TO READ, WRITE, AND MODIFY, CAUSING DEVELOPMENT AND MAINTENANCE COSTS TO INCREASE AT AN EXAGGERATED RATE
While I agree that PI-support is desirable in this area, this is not really a killer argument in my current project scenario. And from what I have heard this issue is going to be addressed in EF V2.
EXCESSIVE MERGE CONFLICTS WITH SOURCE CONTROL IN TEAM ENVIRONMENTS
This is true, that was one of the first things I noticed when I got introduced to the Entity Framework.
But hey guys, this is only version 1.0 of the Entity Framework. To me it still looks promising. Please keep up the good work. And you have a Vote of Confidence from me!