Support partial loading (i.e. not eagerly loading all scalar properties)

[lvasiliou]

Can you please add partial loading and by that I mean in addition to lazy and eager loading of relationships, the third option - lets call it partial for now - loads the related entity but only containing the primary keys and no other data. If needed I could resolve the rest of the data manually.
For example I have a Contact entity with one to many relationship with Address. With partial loading, I will get Contact.Address.AddressId only. I could then resolve the rest of the properties manually. Maybe all maybe the ones I specify via DbContext.Entry(address).Resolve(a=>a.Line1;....

[ajcvickers]

See #9385 for some more ideas in this area.

[ajcvickers]

See #8138 for additional ideas in this area--specifically around lazy loading of scalar properties.

[faibistes]

As a workaround (and that's good enough for me), I do something like this:
Let's assume we have a "estado" table with the field Id as PK and a big text column called "observaciones". This is how you define the entities:

public partial class Estado
{
	public Guid Id { get; set; }
	public DateTime Fecha { get; set; }
	public Observaciones Observaciones { get; set; }
}
public class Observaciones
{
	public Guid Estado { get; set; }
	public string Texto { get; set; }
	public Estado Estado { get; set; }
}
modelBuilder.Entity<Observaciones>(entity =>
{
	entity.HasKey(e => e.Id)
		.HasName("PK_estado");
	entity.HasOne(e => e.Estado).WithOne(o => o.Observaciones).HasForeignKey<Estado>(e => e.Id);
	entity.Property(e => e.Texto)
		.HasColumnName("observaciones")
		.HasColumnType("text");
	entity.ToTable("estado", "reactivos");
});
modelBuilder.Entity<Estado>(entity =>
{
	entity.HasKey(e =>  e.Id)
		.HasName("PK_estado");
	entity.ToTable("estado", "reactivos");
	entity.Property(e => e.Id).HasColumnName("id");
	entity.Property(e => e.Fecha).HasColumnName("fecha");
	entity.HasOne(e => e.Observaciones).WithOne(o => o.Estado).HasForeignKey<Observaciones>(e => e.Id);
});

This works with EF 2.0 (you need to Include() to load observaciones column) I guess that this will lazy load if you define Observaciones and Estado as virtual in EF 2.1, but I haven't tested it.

[bbrandt]

@faibistes Does this produce one query or 2 queries against the same table? If one query, is the table joining with itself on the Id? Any issues from this?