Entity Framework: I set the foreign key, SaveChanges then access the navigation property, but it doesn't load the related entity. Why not?

Question

I am using this Entity class with Entity Framework 5 Code First:

public class Survey
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public i         


        

Answer 1

Like @NicholasButler said, calling SaveChanges does what it says on the tin - you can see this if you debug your code: the Intellitrace output will show the SQL it has generated for the insert/update you are persisting, but there will be no subsequent select.

Keep in mind that unless you are eager loading (using the Include method), related entities are not loaded when performing a retrieval, so it stands to reason that creating/updating them wouldn't either.

The Entity Framework (from I think versions 4.1 and up) supports lazy loading. What this means is that if it's enabled, code like Client c1 = entity.Client; should load up that Client object. To be clear, this operation is not directly related to the SaveChanges call.

It would pay to check whether db.Configuration.LazyLoadingEnabled is set to true. If not, try setting it to be true and see if Client c1 = entity.Client; is still null.

In short, calling SaveChanges does not trigger a load, but if lazy loading is enabled, accessing entity.Client should trigger a load of the entity if it hasn't already been loaded.

Edit:

I should've though of this earlier, but you aren't going to be getting lazy loading on your Survey entity object. The reason is that EF works its lazy loading magic by creating a class derived from your one but overriding the properties marked as virtual to support lazy loading. It does this when you perform a retrieval, so your entity object will not lazy load anything as it stands.

Try this just after your call to SaveChanges:

Survey entity2 = db.Surveys.Find(entity.ID);
Client c1 = entity2.Client;

This should exhibit the behaviour you are after.