EF FluentAPI 0..1 to * mapping

How do I map a 0..1 to * relation in EF 4.0 FluentAPI CTP5? I keep geting this error

Because all of the properties in the Dependent Role are non-nullable, multiplicity of the Principal Role must be '1'.

And I do not know how exactly to fix it..

My code looks like this

    public class Child{
        public int pID { get; set; }
        public Parent Parent_Object{ get; set; } 
        public int Parent{ get; set; } 

        public Child() {
        }
    }


    public class Parent {
        public int pID { get; set; }
        public List<Child>  Children { get; set; }

        public Parent () {
        }
    }

For mapping the code looks lik开发者_如何学编程e this

modelBuilder.Entity<Child>().HasKey(c=> c.pID);  
modelBuilder.Entity<Parent>().HasKey(c=> c.pID); 
modelBuilder.Entity<Child>().HasOptional(c=> c.Parent_Object)
                            .WithMany(p => p.Children)
                            .HasForeignKey(p => p.Parent);

Also is it possible to have only

public Parent Parent{ get; set; } 

instead of

public Parent Parent_Object{ get; set; } 
public int Parent{ get; set; } 

In the database the FKfield is named "Parent" not "ParentpID". In this case how should the mapping look like?

---

You can simply remove Foreign Key Column from the mapping and everything will work fine:

  public class Child{
    public int pID { get; set; }
    public Parent Parent_Object{ get; set; } 

    public Child() { }
  }


  public class Parent {
    public int pID { get; set; }
    public List  Children { get; set; }

    public Parent () { }
  }

  public class Context : DbContext {

    protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder) {

      modelBuilder.Entity().HasKey(c => c.pID);
      modelBuilder.Entity().HasKey(c => c.pID);  
      modelBuilder.Entity().HasOptional(c => c.Parent_Object).WithMany(p => p.Children);
    }

    public DbSet Parents { get; set; }
    public DbSet Childs { get; set; }
  }

As an alternative, you can use the nullable int Parent property, like this:

public int? ParentId { get; set; }  

In this case your initial code will be correct as well.