Question

I’m using entity framework 5.
I’m trying to lazy load an entity collection, I stripped the model to the bare bones to have a simple runable sample.

This is my model:

public class A
{

    public int Id { get; set; }

    public EntityCollection<B> Bs
    {
        get { return bs; }
        set { bs = value; }
    }
    private EntityCollection<B> bs;

    public A()
    {
        bs = new EntityCollection<B>();
    }
}

public class B
{
    public int Id { get; set; }
    public A A { get; set; }
}

public class DbModel : DbContext
{
    public DbSet<A> As { get; set; }
    public DbSet<B> Bs { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<A>()
                    .HasKey( t => t.Id )
                    .HasMany(a => a.Bs)
                    .WithRequired(b => b.A);
        modelBuilder.Entity<A>()
                    .Property(t => t.Id)
                    .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

        modelBuilder.Entity<B>()
                    .HasKey(b => b.Id)
                    .HasRequired(b => b.A);
        modelBuilder.Entity<B>()
                    .Property( t => t.Id )
                    .HasDatabaseGeneratedOption( DatabaseGeneratedOption.Identity );
    }

This is the test demonstrating my problem:

   [TestInitialize]
    public void Initialize()
    {
        model = new DbModel();
        model.Configuration.ProxyCreationEnabled = false;

        if (model.Database.Exists()) model.Database.Delete();

        model.Database.Create();
        A a = model.As.Create();
        model.As.Add(a);
        B b = model.Bs.Create();
        a.Bs.Add(b);

        model.ChangeTracker.DetectChanges();
        model.SaveChanges();
    }

   [TestMethod]
    public void TestMethod1()
    {
        // arrange
        DbModel tModel = new DbModel();
        A a = tModel.As.First();

        // act
        a.Bs.Load();
    }

This is the result:

Test method TestProject1.UnitTest1.TestMethod1 threw exception:

System.InvalidOperationException: Requested operation is not allowed
when the owner of this RelatedEnd is null. RelatedEnd objects that
were created with the default constructor should only be used as a
container during serialization.

Answer 1

As it turns out I was using classes from different paradigms of the ADO family.
As pointed out by Gert Arnold EF doesn’t work with EntityCollection it uses a plain list for association collections.

public class A
{

    public int Id { get; set; }

    public List<B> Bs
    {
        get { return bs; }
        set { bs = value; }
    }
    private List<B> bs = new List<B>();
}

As I did not want the proxies, the objects have no “knowledge” of the model. So the model itself has to be used to load associations for an entity.
For this sample I added the following method to the model:

public class DbModel : DbContext
{
    public DbSet<A> As { get; set; }
    public DbSet<B> Bs { get; set; }

//…

    public A LoadAWithAssociations(A targetA)
    {
        return As.Include("Bs").First(a => a.Id.Equals(targetA.Id));
    }
}

I adapted the test to use the new method

  [TestMethod]
    public void TestMethod1()
    {
        // arrange
        DbModel tModel = new DbModel();
        A a = tModel.As.First();

        // act
        A result =  tModel.LoadAWithAssociations(a);

        // assert 
        Assert.IsNotNull(result);
        Assert.IsTrue(result.Bs.Count > 0);
    }

It gives a green now