Why is a shadow property being generated when this model implements IEnumerable? - entity-framework

Question

I have the following model classes:
public class Farmer
{
public int ID { get; set; }
public Box Box { get; set; }
}
public class Apple
{
public int BoxID { get; set; }
public Box Box { get; set; }
public int Number { get { return (int)V2.X; } set { V2 = new Vector2(value, 0); } }
public Vector2 V2 {get;set;}
public Farmer Owner { get; set; }
}
public class Box : IEnumerable<Apple>
{
public int ID { get; set; }
public ICollection<Apple> Apples { get; set; }
public IEnumerator<Apple> GetEnumerator()
{
return Apples.GetEnumerator();
}
IEnumerator IEnumerable.GetEnumerator()
{
return Apples.GetEnumerator();
}
}
When Box implements IEnumerable<'Apple'>, the shadow property FarmerID is added to the Apple table:
migrationBuilder.AddColumn<int>(
name: "FarmerID",
table: "Apples",
nullable: true);
migrationBuilder.CreateIndex(
name: "IX_Apples_FarmerID",
table: "Apples",
column: "FarmerID");
migrationBuilder.AddForeignKey(
name: "FK_Apples_Farmers_FarmerID",
table: "Apples",
column: "FarmerID",
principalTable: "Farmers",
principalColumn: "ID",
onDelete: ReferentialAction.Restrict);
When I comment out the IEnumerable implementation, the expected migration is created without the FarmerID shadow property. Why is this shadow property being generated and how can I remove it? (I've tried ignoring it, but then I end up getting FarmerID1).
I should mention this is my context class:
public class Context : DbContext
{
public DbSet<Farmer> Farmers { get; set; }
public DbSet<Apple> Apples { get; set; }
public DbSet<Box> Boxes { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlServer(#"...");
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Apple>()
.HasOne(a => a.Box)
.WithMany(a => a.Apples)
.IsRequired();
modelBuilder.Entity<Apple>()
.Ignore(a => a.V2)
.Ignore(a => a.Owner)
.HasKey(a => new { a.BoxID, a.Number });
}
}

Answer 1

The problem is that the ID properties of the Farmer and Box models are not getting mapped which requires EF Core to create a shadow property to Apples to map a farmer to a Box.
To solve the problem, the following can be done:
Rename ID to Id. EF core uses very specific naming conventions to map properties, even in constructors, so if the properties are not named according to the convention expected by EF Core, it will fail.
Add [Key] to ID.
Use Fluent API .HasKey to specify the Key.