I'm tempted to answer Mu, but I'd like to elaborate. In summary: Don't let your choice of ORM dictate how you define your Domain Model.
The purpose of the Domain Model is to be a rich object-oriented API that models the domain. To follow true Domain-Driven Design, the Domain Model must be defined unconstrained by technology.
In other words, the Domain Model comes first, and all technology-specific implementations are subsequently addressed by mappers that map between the Domain Model and the technology in question. This will often include both ways: to the Data Access Layer where the choice of ORM may introduce constraints, and to the UI layer where the UI technology imposes additional requirements.
If the implementation is extraordinarily far from the Domain Model, we talk about an Anti-Corruption Layer.
In your case, what you call an Anemic Domain Model is actually the Data Access Layer. Your best recourse would be to define Repositories that model access to your Entities in a technology-neutral way.
As an example, let's look at your Order Entity. Modeling an Order unconstrained by technology might lead us to something like this:
public class Order
{
// constructors and properties
public decimal CalculateTotal()
{
return (from li in this.LineItems
select li.CalculateTotal()).Sum();
}
}
Notice that this a Plain Old CLR Object ( POCO ) and is thus unconstrained by technology. Now the question is how you get this in and out of your data store?
This should be done via an abstract IOrderRepository:
public interface IOrderRepository
{
Order SelectSingle(int id);
void Insert(Order order);
void Update(Order order);
void Delete(int id);
// more, specialized methods can go here if need be
}
You can now implement IOrderRepository using your ORM of choice. However, some ORMs (such as Microsoft's Entity Framework) requires you to derive the data classes from certain base classes, so this doesn't fit at all with Domain Objects as POCOs. Therefor, mapping is required.
The important thing to realize is that you may have strongly typed data classes that semantically resemble your Domain Entities. However, this is a pure implementation detail, so don't get confused by that. An Order class that derives from e.g. EntityObject is not a Domain Class - it's an implementation detail, so when you implement IOrderRepository, you need to map the Order Data Class to the Order Doman Class.
This may be tedious work, but you can use AutoMapper to do it for you.
Here's how an implementation of the SelectSingle method might look:
public Order SelectSinge(int id)
{
var oe = (from o in this.objectContext.Orders
where o.Id == id
select o).First();
return this.mapper.Map<OrderEntity, Order>(oe);
}
