Using Entity Framework Code First, I'm seeing very strange behavior when inserting a row with a composite key. The composite key consists of a guid ID field and a guid foreign key field, creating an "identifying relationship". The strange behavior is that regardless of what I set the ID and foreign key field to, the generated SQL sets them both to the foreign key value.
My classes look like this:
public class Parent {
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public Guid Id { get; set; }
public ICollection<Child> Children { get; set; }
}
public class Child {
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public Guid Id { get; set; }
public Guid ParentId { get; set; }
}
In my DbContext file I have:
modelBuilder.Entity<Child>().HasKey(c => new { c.Id, c.ParentId });
Doing something like:
var parent = new Parent() { Id = Guid.NewGuid() };
var child = new Child() { Id = Guid.NewGuid(), ParentId = parent.Id };
parent.Children.Add(child);
You'd think the SQL executed would insert a new child with differing Id and ParentId values. But instead, what I'm seeing is:
// Assume parent is already in the DB, with ID of '1b1a6ecd-00ad-4265-ac0d-9a50bd30e247'
INSERT [dbo].[Child]
([Id],
[ParentId])
VALUES ('1b1a6ecd-00ad-4265-ac0d-9a50bd30e247' /* @0 */,
'1b1a6ecd-00ad-4265-ac0d-9a50bd30e247' /* @1 */)
Why is the SQL using the ParentId value for both fields? This doesn't make sense at all.
UPDATE
Unless I totally misunderstand something fundamental to EF, I think this must be a bug. I've uploaded a tiny reproducible project to http://1drv.ms/1kX2oVC
It uses EF 6.1 and .NET 4.5. I'm hoping some EF expert can chime in here and confirm this is a bug, or that I'm doing something fundamentally wrong.