title: 'PK_dbo.EntityName' is not a constraint. Could not drop constraint.EF6
body: <p>I'm using Entity Framework 6 code first. I have three Entity like these :</p>
  
  <pre><code>public class Doctor
  {
      public string DoctorID { get; set; } 
      public string firstName { get; set; }
      public string lastName { get; set; }
   }
  
  public class ExpertiseDetails
  {
      [Key, Column(Order = 1)]
      public short expertiseID { get; set; }
      [Key , Column(Order = 2)]
      public string DoctorID { get; set; }
  
      [ForeignKey("expertiseID")]
      public Expertise expertise { get; set; }
      public Doctor doctor { get; set; }
  }
  
  
  public class Expertise
  {
      [Key]
      public short expertiseID { get; set; }
      public string expertiseTitle { get; set; }
  }
  </code></pre>
  
  <p>I need a <code>one to many</code> realationship between <code>Expertise</code> and <code>Doctor</code>,When I run update-database statement in console <code>nuGet</code> this error shows :</p>
  
  <pre><code>'PK_dbo.ExpertiseDetails' is not a constraint. Could not drop constraint
  </code></pre>
  
  <p>What's wrong ?</p>