Should one use DI on POCO classes when doing DDD?

Question

Say I have a nice domain model, using (constructor) DI where needed. Now I want to be able to persist this model, so I start adding infrastructure(Entity Framework) to do this. What happens now is that the persistence framework should be able to initialize your types using your IoC container.

Maybe this is possible, maybe not. Anyway, what I'm wondering now is; is it usual to use DI on you POCO classes at all? And if it is, how do I make Entity Framework use my favorite IoC container(in my case NInject) to construct my classes.

Answer 1

It is more than OK to use IoC container to construct entities fetched from the database, I do that in my project.

ORM should not dictate your design. NHibernate can play nice with IoC Container, I have no idea about EF but I suspect it does not. I'd swap EF for NHibernate, or actually anything else if I were you.

Answer 2

This is one of the religious arguments in the DDD community: should I inject services into my entities? It's really a question that you'll have to answer yourself. I"m not going to tell you what I think because it's highly contextual - what I think changes depending on several factors.

I do think you need to take a few hours and really dig deep into the archives of the ddd list to establish an answer that will work for you.

Answer 3

I you would like to use EF so consider EF4 where you can use POCO templates indeed. You can implement Repositories around your POCO classes and you will be able to use IoC as you use it with another ORM. Whan you have POCO it's all about application architecture layaring.

Look at this walktrough:

http://blogs.msdn.com/adonet/pages/walkthrough-poco-template-for-the-entity-framework.aspx