Convince entity context (EF1) to populate entity references

Question

I have an entity with self reference (generated by Entity Designer):

public MyEntity: EntityObject
{
    // only relevant stuff here
    public int Id { get...; set...; }
    public MyEntity Parent { get...; set...; }
    public EntityCollection<MyEntity> Children { get...; set...; }
    ...
}

I've written a stored procedure that returns a subtree of nodes (not just immediate children) from the table and returns a list of MyEntity objects. I'm using a stored proc to avoid lazy loading of an arbitrary deep tree. This way I get relevant subtree nodes back from the DB in a single call.

List<MyEntity> nodes = context.GetSubtree(rootId).ToList();

All fine. But when I check nodes[0].Children, its Count equals to 0. But if I debug and check context.MyEntities.Results view, Children enumerations get populated. Checking my result reveals children under my node[0].

How can I programaticaly force my entity context to do in-memory magic and put correct references on Parent and Children properties?

UPDATE 1

I've tried calling

context.Refresh(ClientWins, nodes);

after my GetSubtree() call which does set relations properly, but fetches same nodes again from the DB. It's still just a workaround. But better than getting the whole set with context.MyEntities().ToList().

UPDATE 2

I've reliably solved this by using EF Extensions project. Check my answer below.

Answer 1

You need to assign one end of the relationship. First, divide the collection:

var root = nodes.Where(n => n.Id == rootId).First();
var children = nodes.Where(n => n.Id != rootId);

Now, fix up the relationship.

In your case, you'd do either:

foreach (var c in children)
{
    c.Parent = root;
}

...or:

foreach (var c in children)
{
    root.Children.Add(c);
}

It doesn't matter which.

Note that this marks the entities as modfied. You'll need to change that if you intend to call SaveChanges on the context and don't want this saved.

Answer 2

The REAL solution

Based on this article (read text under The problem), navigation properties are obviously not populated/updated when one uses stored procedures to return data.

But there's a nice manual solution to this. Use EF Extensions project and write your own entity Materilizer<EntityType> where you can correctly set navigation properties like this:

...
ParentReference = {
    EntityKey = new EntityKey(
        "EntityContextName.ParentEntitySetname",
        new[] {
            new EntityKeyMember(
                "ParentEntityIdPropertyName",
                reader.Field<int>("FKNameFromSP")
            )
        })
}
...

And that's it. Calling stored procedure will return correct data, and entity object instances will be correctly related to eachother. I advise you check EF Extensions' samples, where you will find lots of nice things.