EF FluentAPI 0..1 to * mapping - foreign-keys

Question

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 like 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?

Answer 1

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.