CODEWITHSUNDEEP
c#entity-frameworkado.net
gerrod
gerrod

Reputation: 6627

Entity Framework references not loading automatically

In the ADO.Net Entity Framework, I have an object which has 4 references to other objects. For some reason, when I query those references, two of them load automatically (as expected), and two of them always return null.

Bizarrely enough, when I manually ask the references to load, they load just dandy.

As an example:

if (account.HoldingEntity == null && 
    account.HoldingEntityReference.EntityKey != null) {

    account.HoldingEntityReference.Load();
    account.HoldingEntity = account.HoldingEntityReference.Value;
}

When I first check the HoldingEntity it is always null, however the Load will return the HoldingEntity without problem.

Any clues?

Thanks!

Upvotes: 7

Views: 8430

Answers (3)

Alex James
Alex James

Reputation: 20914

As others have said you need to .Include() in v1 to avoid needing to call .Load()

In 4.0 you will be able to set DeferredLoadingEnabled on your ObjectContext (I think we are changing this name to the more appropriate LazyLoadingEnabled in time for Beta2).

As for why you get 2 relationships already loaded anyway. That is probably a side-effect of something called Relationship Fix-up.

When two related entities are in the same Context, they automatically get their relationship's fixed to point to each other. So if (as I suspect) 2 of the 4 entities are already in your context, when you do the query, you will end up in a situation where 2 of your relationships are loaded, even though you didn't call .Include() or .Load().

Hope this helps

Cheers Alex

Upvotes: 5

marc_s
marc_s

Reputation: 754230

This was done in EF v1 as a design decision, and many developers actually prefer having explicit control over if and when referenced properties will be loaded.

For EF v4 coming out with .NET 4.0 before the end of 2009, you'll have the option to turn on automatic deferred loading, if you so wish. See this blog post on the ADO.NET team blog for more information on deferred loading in EF v4.

Marc

Upvotes: 0

Paulo Santos
Paulo Santos

Reputation: 11567

Using ADO.NET Entities, you need to specify what entities you want to load automatically with Include, as in

Dim entity = (From e in db.Entities.Include("SubEntity"))

Upvotes: 7

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