title: entity framework code first - Union of the two fields into one collection
body: <p>i have this model and configuration </p>
  
  <pre><code>public class Person
   {
       public int? FatherId { get; set; }
       public virtual Person Father { get; set; }
       public int? MotherId { get; set; }
       public virtual Person Mother { get; set; }
       public virtual List&lt;Person&gt; Childs { get; set; }
  
   }
   class PersonConfiguration : EntityTypeConfiguration&lt;Person&gt;
   {
       public PersonConfiguration()
       {
           HasOptional(e =&gt; e.Father).WithMany(e =&gt; e.Childs)
                .HasForeignKey(e =&gt; e.FatherId);
           HasOptional(e =&gt; e.Mother).WithMany(e =&gt; e.Childs)
                .HasForeignKey(e =&gt; e.MotherId);
       }
   }
  </code></pre>
  
  <p>and i get  this error where the type is initial.</p>
  
  <blockquote>
    <p>Schema specified is not valid. Errors:  (151,6) : error 0040: Type
    Person_Father is not defined in namespace ExamModel (Alias=Self).</p>
  </blockquote>
  
  <p>Is there a way to map <code>Childs</code> property by both properties (motherId and fatherId)?</p>