c#-4.0 - Entity オブジェクトは、IEntityChangeTracker の複数のインスタンスで参照できません

Question

私は以下のPOCOクラスを持っています。

public class AppointmentModel
        {
          public InvoiceDetail InvoiceDetails { get; set; }
          public Invoice Invoice { get; set; }
        }


public class InvoiceDetail
    {
       public Invoice Invoice { get; set; }

    }



public class Invoice
    {
        public Invoice()
        {
            Id = Guid.NewGuid(); Created = DateTime.Now;
        }
        public Guid Id { get; set; }

        public virtual Appointment Appointment { get; set; }

}

そのモデルをリポジトリ内に追加しようとしましたが、以下のとおりです。

public void Booking(AppointmentModel appointmentModel)
        {

                appointmentModel.InvoiceDetails.Invoice.LatestTotal = latestinvoiceTotal;
                Catalog.Appointments.Add(appointmentModel.InvoiceDetails.Invoice.Appointment);
                 Catalog.SaveChanges();
        }

以下のエラーが発生します。

エンティティ オブジェクトは、IEntityChangeTracker の複数のインスタンスによって参照できません

スタックトレースは以下の通りです。

   at System.Data.Objects.ObjectContext.VerifyContextForAddOrAttach(IEntityWrapper wrappedEntity)
   at System.Data.Objects.ObjectContext.AddSingleObject(EntitySet entitySet, IEntityWrapper wrappedEntity, String argumentName)
   at System.Data.Objects.DataClasses.RelatedEnd.AddEntityToObjectStateManager(IEntityWrapper wrappedEntity, Boolean doAttach)
   at System.Data.Objects.DataClasses.RelatedEnd.AddGraphToObjectStateManager(IEntityWrapper wrappedEntity, Boolean relationshipAlreadyExists, Boolean addRelationshipAsUnchanged, Boolean doAttach)
   at System.Data.Objects.DataClasses.RelatedEnd.IncludeEntity(IEntityWrapper wrappedEntity, Boolean addRelationshipAsUnchanged, Boolean doAttach)
   at System.Data.Objects.DataClasses.EntityReference`1.Include(Boolean addRelationshipAsUnchanged, Boolean doAttach)
   at System.Data.Objects.DataClasses.RelationshipManager.AddRelatedEntitiesToObjectStateManager(Boolean doAttach)
   at System.Data.Objects.ObjectContext.AddObject(String entitySetName, Object entity)
   at System.Data.Entity.Internal.Linq.InternalSet`1.<>c__DisplayClass5.<Add>b__4()
   at System.Data.Entity.Internal.Linq.InternalSet`1.ActOnSet(Action action, EntityState newState, Object entity, String methodName)
   at System.Data.Entity.Internal.Linq.InternalSet`1.Add(Object entity)
   at System.Data.Entity.DbSet`1.Add(TEntity entity)
   at PawLoyalty.Data.PetBookings.Repositories.InvoiceRepository.Booking(AppointmentModel appointmentModel) in d:\PawLoyalty Module\New Booking Flow\NewBookingFlow\PawLoyalty\PawLoyalty.Data\PetBookings\Repositories\InvoiceRepository.cs:line 339
   at PawLoyalty.Business.Invoices.InvoiceService.Booking(AppointmentModel appointmentModel) in d:\PawLoyalty Module\New Booking Flow\NewBookingFlow\PawLoyalty\PawLoyalty.Business\Invoices\InvoiceService.cs:line 38
   at PawLoyalty.Business.BookingFacadeService.Booking(AppointmentModel appointmentModel) in d:\PawLoyalty Module\New Booking Flow\NewBookingFlow\PawLoyalty\PawLoyalty.Business\BookingFacadeService.cs:line 152
   at PawLoyalty.Web.Controllers.PetBookingController.BookingProcess(String providerKey, String ownerKey, String serviceId, String petKeys, String selectedDates, String selectedExtraServices, String selectedResourceId, String key, String type) in d:\PawLoyalty Module\New Booking Flow\NewBookingFlow\PawLoyalty\PawLoyalty.Web\Controllers\PetBookingController.cs:line 243
   at lambda_method(Closure , ControllerBase , Object[] )
   at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass42.<BeginInvokeSynchronousActionMethod>b__41()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass37.<>c__DisplayClass39.<BeginInvokeActionMethodWithFilters>b__33()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49()

アップデート

BasicRepository は以下の通りです。すべてのリポジトリはこれから継承されています。

 public class BasicRepository : IBasicRepository
    {
        private DataCatalog catalog;
        protected DataCatalog Catalog { get { if (catalog == null) catalog = new DataCatalog(); return catalog; } }
        public void Dispose() { if (catalog != null) catalog.Dispose(); }

}

助けてもらえますか？