What is the syntax for self referencing foreign keys in EF Code First?

Question

I am trying to reference a foreign key from SpouseId to Id in the Contact table. What is the syntax for doing this? I can't seem to find an example. Thanks.

I have a class like this:

public class Contact {     public int Id {get;set;}     public string Name {get;set;}     public int? SpouseId {get;set;} } 

EDIT1 Per the link provided by Joel Cunningham and the answer from Morteza I have added some additional code.

ContactMap.cs

public partial class ContactMap : EntityTypeConfiguration<Contact> {   public ContactMap()      {        this.ToTable("Contact");        this.HasKey(c => c.Id);        this.HasOptional(c => c.Spouse)            .WithMany()            .IsIndependent()            .Map(m => m.MapKey(fk => fk.Id, "SpouseId"));      } } 

MyObjectContext.cs

public class MyObjectContext : DbContext, IDbContext {   public DbSet<Contact> Contacts {get;set;}   protected override void OnModelCreating(ModelBuilder modelBuilder)      {         modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();         modelBuilder.Configurations.Add(new ContactMap());      } } 

Note: I also added the "[ForeignKey("SpouseId")]" attribute to my Spouse property in my Contact class. Unfortunately I keep getting "Sequence contains more than one matching element".

EDIT2: Morteza's answers below is correct. To summarize: For self referencing foreign keys you can either mark the property as a "[ForeginKey("SpouseId")] OR use the fluent API example below. The errors I reported in some of my comments were caused by my unit test. EF generated the db the correct way. I found a good link where Craig Stuntz outlined why auto-increment keys and self-referencing foreign keys can cause the "Unable to determine a valid ordering for dependent operations" error. I believe this is what my problem is. Hope this helps someone.

Answer 1

Something like this will work:

public class Contact {     public int Id {get;set;}     public string Name {get;set;}     public int? SpouseId {get;set;}      [ForeignKey("SpouseId")]     public Contact Spouse {get;set;} } 

ForeignKeyAttribute has been added to System.ComponentModel.DataAnnotations by CTP5 assembly.

Update I: CTP5 Bug:

Due to a bug in CTP5, creating an Independent Self Referencing Associations throws an exception. The workaround is to use Foreign Key Associations instead (which is always recommended regardless).

Update II: Using Fluent API to Configure a Self Referencing Association:

You can also use fluent API to achieve this, if you prefer:

public class Contact {     public int Id { get; set; }     public string Name { get; set; }     public int? SpouseId { get; set; }                      public Contact Spouse { get; set; } }  public class Ctp5Context : DbContext {     public DbSet<Contact> Contacts { get; set; }      protected override void OnModelCreating(ModelBuilder modelBuilder)     {         modelBuilder.Entity<Contact>()                     .HasOptional(c => c.Spouse)                     .WithMany()                     .HasForeignKey(c => c.SpouseId);     } } 

Working with the Model:

using (var context = new Ctp5Context()) {     Contact contact = new Contact()     {         Name = "Morteza",         Spouse = new Contact()         {             Name = "Code-First"         }     };     context.Contacts.Add(contact);     context.SaveChanges(); }