title: How to allow null values on Foreign keys using EF?
body: <p>How to allow null values on Foreign keys using EF?</p>
  
  <pre><code>public class User
  {
      public User() 
      { 
      }
  
      public int idUser; { get; set; }
      [Required]
      public string UserName { get; set; }
      public virtual Computer Computer{ get; set; }
  }
  
  public class Computer
  {
      public Computer() 
      {
      }
      [Key, ForeignKey("User")]
      public int idUser{ get; set; }
      public string ComputerName {get;set;}
      public virtual User User { get; set; }
  }
  </code></pre>
  
  <p>Running this I'm getting <code>not null</code> on the foreign key.</p>