Question

I have 2 classes:

public class FlightCostInfo : BaseEntity<Guid>
{
  public Flight FlightInfo { get; set; }
  public virtual ICollection<Cost> Costs { get; set; }
  public virtual ICollection<PriceCalculationNotification> Notifications { get; set; }
  public Guid CalculationResultId { get; set; }
}

public class Cost : BaseEntity<Guid>
{
  public BasePrice Price { get; set; }
  public decimal Amount { get; set; }
  public Vendor Vendor { get; set; }
  public Guid FlightCostInfoId { get; set; }
}

And mapping for them:

internal class FlightCostInfoMapping : EntityTypeConfiguration<FlightCostInfo>
    {
        public FlightCostInfoMapping()
        {
            HasKey(i => i.Id);
            Property(i => i.CalculationResultId).HasColumnName("CalculationResult_Id");
            HasOptional(i => i.FlightInfo);
            HasMany(i => i.Costs).WithRequired().HasForeignKey(c => c.FlightCostInfoId);
            HasMany(i => i.Notifications).WithRequired().HasForeignKey(n => n.FlightCostInfoId);
        }
    }

internal class CostMapping : EntityTypeConfiguration<Cost>
{
    public CostMapping()
    {
        HasKey(c => c.Id);
        Property(c => c.FlightCostInfoId).HasColumnName("FlightCostInfo_Id");
        HasRequired(c => c.Price);
        HasRequired(c => c.Vendor);
    }
}

When I’m saving List of FlightCostInfo where each contains one or more Cost objects I recieve following error:

Multiplicity constraint violated. The role FlightCostInfo_Costs_Source of the relationship Charges.Infrastructure.DataAccess.FlightCostInfo_Costs has multiplicity 1 or 0..1

I don’t have any idea why this happens. Could anyone help?

Update:
Code to save list of FlightCostInfo:

        public virtual void Save(IEnumerable<TObject> entities)
        {
            Context.Configuration.AutoDetectChangesEnabled = false;
            entities.ToList().ForEach(entity => 
            {
                if (Equals(entity.Id, default(TKey)) || !Context.ChangeTracker.Entries<TObject>().ToList().Any(dbEntry => dbEntry.Entity.Id.Equals(entity.Id)))
                {
                    Set.Add(entity);
                }
            });

            Context.ChangeTracker.DetectChanges();
            SaveChanges();
            Context.Configuration.AutoDetectChangesEnabled = true;
        }

        protected void SaveChanges()
        {
            var entriesWithGuidKey = Context.ChangeTracker.Entries<BaseEntity<Guid>>().Where(e => e.Entity.Id == Guid.Empty).ToList();
            entriesWithGuidKey.ForEach(e => e.Entity.Id = Guid.NewGuid());

            var entriesWithPeriodicValidity = Context.ChangeTracker.Entries<IPeriodicValidityObject>().ToList();
            entriesWithPeriodicValidity.ForEach(e => 
                {
                   if (e.State != System.Data.EntityState.Unchanged)
                   {
                       e.Entity.ChangedDate = DateTime.UtcNow;
                   }
                });
            Context.SaveChanges();
        }

Answer 1

The problem appeared to be in Equals overload for BaseEntity. So EF thought that all Cost objects in FlightCostInfo collection are equal.

Closing the question