public Order(OrderId id, string concertId, string userId, IEnumerable <OrderItem> items, IPriceCalculator priceCalculator)
{
if (string.IsNullOrWhiteSpace(concertId))
{
throw new ArgumentException("concert id should not be null", nameof(concertId));
}
Id = id ?? throw new ArgumentNullException(nameof(id));
this.ApplyChange(new OrderPlaced(concertId, userId, items.ToList()));
this.ApplyChange(new OrderTotalCalculated(priceCalculator.Total(items).ToValue()));
}