title: EF Code First Update method does not work
body: <p>i have this class</p>
  
  <pre><code>public class BankAccount : IEntity
  {
      public int Id { get; set; }
      public long AccountNumber { get; set; }
      public string Description { get; set; }
      public bool IsFund { get; set; }
  
      public virtual Person Owner { get; set; }
      public virtual Branch Branch { get; set; }
  
      public BankAccount()
      {
          AccountNumber = 0;
          IsFund = false;
          Description = "Empty";
      }
  }
  </code></pre>
  
  <p>and update method:</p>
  
  <pre><code>public void Update(DBS.BankAccount entity)
  {
      try
      {
          using (var _nahidContext = new NahidContext())
          {
              var bankAccountElement= FindById(entity.Id);
              _nahidContext.Entry(bankAccountElement).State = System.Data.Entity.EntityState.Modified;
              var bankAccount = _nahidContext.Entry(bankAccountElement);
              bankAccount.CurrentValues.SetValues(entity);
              _nahidContext.SaveChanges();
          }
      }
      catch (Exception ex)
      {
          throw new ArgumentException(ex.Message);
      }
  }
  </code></pre>
  
  <p>when i run update method and change (owner,branch,description) value just description does change and owner,branch haven't any change.
  how can i change owner or branch?[Thanks]</p>