EF Core self referencing not working if there are 2 foreign keys to self (Code first)

Question

If I defined (in code first) one navigation property to self it works (foreign key is created), but if I define 2 it doesn't work.
How can I create 2 foreign keys to self? Based on documentation by conventions they should be created.

For example this works (foreign key is created):

public class DbPart 
{
    [Key]
    [Required]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    [ForeignKey("Source")]
    public int? SourceId { get; set; }
    public DbPart Source { get; set; }

    [InverseProperty("Source")]
    public List<DbPart> SourceParts { get; set; }
}

and so is this:

public class DbPart 
{
    [Key]
    [Required]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    [ForeignKey("SourceFake")]
    public int? SourceFakeId { get; set; }
    public DbPart SourceFake { get; set; }

    [InverseProperty("SourceFake")]
    public List<DbPart> SourceFakeParts { get; set; }
}

but not this:

public class DbPart 
{
    [Key]
    [Required]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    [ForeignKey("Source")]
    public int? SourceId { get; set; }
    public DbPart Source { get; set; }


    [ForeignKey("SourceFake")]
    public int? SourceFakeId { get; set; }
    public DbPart SourceFake { get; set; }

    [InverseProperty("SourceFake")]
    public List<DbPart> SourceFakeParts { get; set; }

    [InverseProperty("Source")]
    public List<DbPart> SourceParts { get; set; }
}

I also have another example, where I write tree structure in database, but instead writing just ParentId, I also write RootId. Again, foreign key is not created when referencing 2 properties to self (ParentId, RootId).

Edited:
It is not working because of this bug. Easy solution is to remove [Key] from Id property or use fluent solution in Steve Greene answer. Check also here.

What is the error message? – Steve Greene Oct 19 '17 at 14:21 — Steve Greene, Oct 19 '17 at 14:21
No error, just column is not defined as foreign key. – Makla Oct 19 '17 at 18:57 — Makla, Oct 19 '17 at 18:57

score 4 · Accepted Answer · edited Oct 19 '17 at 19:19

I prefer the fluent code for this stuff:

modelBuilder.Entity<DbPart>()
    .HasOne(p => p.Source)
    .WithMany(p => p.SourceParts)
    .HasForeignKey(p => p.SourceId);

modelBuilder.Entity<DbPart>()
    .HasOne(p => p.SourceFake)
    .WithMany(p => p.SourceFakeParts)
    .HasForeignKey(p => p.SourceFakeId);

But if you want annotations try this:

public class DbPart 
{
    public int Id { get; set; }   // Key & Indentity by convention

    public int? SourceId { get; set; }  // FK by convention
    [InverseProperty("SourceParts")]
    public DbPart Source { get; set; }

    public int? SourceFakeId { get; set; } // FK by convention
    [InverseProperty("SourceFakeParts")]
    public DbPart SourceFake { get; set; }

    [InverseProperty("SourceFake")]
    public List<DbPart> SourceFakeParts { get; set; }

    [InverseProperty("Source")]
    public List<DbPart> SourceParts { get; set; }
}

I prefer annotations. Looks more readable to me. And your idea with annotations is not working (looks like bug). Fluent code works. — Makla, Oct 19 '17 at 19:01
Not working with annotations looks like bug to me, so I post issue on [GitHub](https://github.com/aspnet/EntityFrameworkCore/issues/10123). — Makla, Oct 19 '17 at 19:15

EF Core self referencing not working if there are 2 foreign keys to self (Code first)

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