title: Validation failed for one or more entities. UserManager.AddToRole()
body: <p>I'm developing a Web Api using ASP.NET MVC5 and I have successfully implemented a Custom IdentityUser.Like So</p>
  
  <pre><code>public partial class Authentication : IdentityUser
  {
      public Authentication()
      {
          this.LoginSessions = new List&lt;LoginSession&gt;();
      }
      [Required]
      public string PersonId { get; set; }
      public virtual Lecturer Lecturer { get; set; }
      public virtual Student Student { get; set; }
      public virtual ICollection&lt;LoginSession&gt; LoginSessions { get; set; }
  }
  </code></pre>
  
  <p>with the following Maps</p>
  
  <pre><code>public class IdentityUserLoginConfiguration: EntityTypeConfiguration&lt;IdentityUserLogin&gt;
  {
      public IdentityUserLoginConfiguration()
      {
          HasKey(t =&gt; t.UserId);
      }
  }
  
  public class IdentityRoleConfiguration : EntityTypeConfiguration&lt;IdentityRole&gt;
  {
      public IdentityRoleConfiguration()
      {
          HasKey(t =&gt; t.Id);
      }
  }
  public class AuthenticationMap : EntityTypeConfiguration&lt;Authentication&gt;
  {
      public AuthenticationMap()
      {
  
          // Primary Key
          this.HasKey(t =&gt; t.PersonId);
  
          // Properties
          this.Property(t =&gt; t.PersonId)
              .IsRequired()
              .HasMaxLength(14);
  
          // Table &amp; Column Mappings
          this.ToTable("Authentication");
          this.Property(t =&gt; t.PersonId).HasColumnName("PersonID");
  
          // Relationships
          this.HasOptional(t =&gt; t.Lecturer)
              .WithOptionalPrincipal(t =&gt; t.Authentication);
          this.HasOptional(t =&gt; t.Student)
              .WithOptionalPrincipal(t =&gt; t.Authentication);
  
  
      }
  }
  </code></pre>
  
  <p>But now my problem is that when I'm adding a user to a Role Using the </p>
  
  <pre><code>UserManager.AddToRole()
  </code></pre>
  
  <p>method I get a DBValidationError 
  This is really worrying me and would like some help as soon as possible</p>