Is there a way to tell ef 4.1 which order the properties on an entity should be loaded in?

Question

Say I have an entity Parent, and an entity Child, such that Parent has a virtual ICollection Children property. In the db this is a simple foreign key from the Child table to the Parent table.

Now say I have a scalar string property on Parent called Text. During the set method of the Text property, I want to access instances in the Children collection property.

When EF 4.1 reconstitutes the Parent entity from the db (because of a ToList() call for example), it calls the set method on the Text property, and it always seems to do so before populating the Children collection.

Is there a way to tell EF to call set on the Children virutal collection property before calling set on the Text scalar string property?

The behaviour of your property setters (set `Text` property and set child collection) depends on the order you call them - `x.Text = "a"; x.Children = someChildren;` gives another result than `x.Children = someChildren; x.Text = "a";` no matter if you do it manually or if EF does it during object materialization. Somehow I had a bad feeling with such a property setter. I'd consider to rewrite this code. I don't think that you can influence the internal implementation of entity materialization in EF. — Slauma, Dec 01 '11 at 21:24

score 2 · Accepted Answer · edited May 23 '17 at 11:48

You should follow @Slauma's advice from comment and change the code because this is wrong behavior for persisted properties. Even if following description works it will be highly error prone because you will always have to query data in specific way.

Your problem can be divided into multiple parts based on the way how you load entities.

Lazy loading:

If you load Parent andChild` are lazy loaded you cannot achieve reverse loading.

// Now parent is loaded
var parent = context.Parent.First(); 

// Even with lazy loading enabled and your setter accessing nav. property it
// should not load child collection because lazy loading should be temporarily
// turned off during entity materialization to avoid unexpected lazy loads

(untested) You can try manually load all child first and request parent after that:

// Now all child for given parent are loaded
var child = context.Child.Where(c => c.Parent.Id == ...).ToList();

// Now parent is loaded and if you are lucky it configures navigation property
// to loaded child prior to evaluating your setter - I guess setter will be 
// evaluated prior to fixing navigation properties so it will not work
var parent = child[0].Parent;

The explicit loading will suffer the same issue.

Eager loading:

The problem is the same and it is based on the way how Include works.

So if you include child to parent the parent will be materialized first.

var parent = context.Parent.Include("Child").First();

Reverse operation in this case most probably doesn't help because calling

var childs = context.Child.Include("Parent").Where(...).ToList();

will evaluate records one by one and each record will contain single child and parent so I think the first time you access the parent you will have only single child and again you will be dependent on the order of operation EF does (the same problem as with lazy loading).

Thanks for the explanation. I will change. – danludwig Dec 02 '11 at 13:11 — danludwig, Dec 02 '11 at 13:11

Is there a way to tell ef 4.1 which order the properties on an entity should be loaded in?

1 Answers1