Wide and narrow versions of an entity mapped to one table in Entity Framework

Question

In some scenarios I need a "wide" version of an entity with many properties (say FullCustomer) while in other scenarios it's enough with a "narrow" version with few properties (say MiniCustomer), how could I map these two entities, FullCustomer and MiniCustomer, to the same Customer table in the database? Furthermore, I need to be able to query and update both entities.

Thanks in advance for any advice or pointers!

PD. I'm using VS2010 RC and EF 4

Answer 1

If you have a column that determines whether to treat the record as a FullCustomer or as MiniCustomer, then you can easily create a Table per Hierarchy inheritance model with FullCustomer inherited from MiniCustomer. Such approach is described in the Muhammad Mosa's blog post.
If you don't have this column you can update the model and database in order to add it.
However, there is an alternative approach. If the reason to have two entities for one table is the delay in the loading the numerous large properties in the FullCustomer object, than Table Splitting might be an option. Take a look at the Julie Lerman's blog post.
I would have noted that this problem is not present in ORMs like LINQ to SQL, due to deferred loading.

Answer 2

For "efficiency", don't have two versions of the entity; just project onto "lite" POCOs:

var q = from e in Context.Entities
        select new LitePoco
        {
            Id = e.Id,
            EditThis = e.EditThis
        };

No other columns will be returned.

Similarly for save:

var e = new MyEntity { Id = 123 };
Context.AttachTo("Entities", e);
// anything from here on gets saved
e.EditThis = "Edited";
Context.SaveChanges();