Entity Framework - Navigating and Including properties through collections

Question

I've just had a massive blonde moment*, but it's highlighted an annoyance I have with Entity Framework. I have disabled lazy loading so I'm forcing myself to actually think about what data I require in order to keep the application as fast as possible.

So in order to return data within a query, I need to make use of the Include method:

var query = from item in context.Customers
                .Include(x=> x.Orders)
            select item

This is fine until I want to select an item a bit deeper into the hierarchy. I.e:

Customer 1-* Orders *-1 Factory 1-1 Factory Type

As far as I know, the only way to return all this data eagerly would be to do the following:

var query = from item in context.Customers
                .Include("Orders.Factory.FactoryType")
            select item

With the above I'm unable to make use of the System.Data.Entity Lambdas as per my first example. Does anyone know if I'm missing something obvious here, or am I stuck with using string declarations for my navigation properties through collections?

If I didn't have any collections, I could just write:

.Include(x=> x.Order.OrderType.Factory.FactoryType) // No bother

But because of the Orders collection, there's no way to step through to a child property as far as I can tell (FirstOrDefault, SingleOrDefault, etc, do not work).

---

*it's just a turn-of-phrase, I happen to be very fond of blondes

Answer 1

For including EntityCollections you use the Select method:

var query = from item in context.Customers
           .Include(c => c.Orders.Select(o => o.Factory.FactoryType))
           select item

Please note that this is not an overload of the standard ObjectQuery<T>.Include Method and is merely an extension method on ObjectQuery<T> Class coming with EF CTP4.