public Order(string id,
string userId,
IEnumerable <string> productsIds,
ProductsCatalog productsCatalog)
{
Id = id ?? throw new ArgumentNullException(nameof(id));
UserId = userId ?? throw new ArgumentNullException(nameof(userId));
ProductsIds = productsIds ?? throw new ArgumentNullException(nameof(productsIds));
_productsCatalog = productsCatalog ?? throw new ArgumentNullException(nameof(productsCatalog));
}
public static IObservable <Product> FindMostExpansivePurchase(
IObservable <Order> ordersHistory,
ProductsCatalog productsCatalog)
{
IObservable <Product> allOrdersProducts =
ordersHistory.SelectMany(order => order.ProductsIds.Select(id => productsCatalog.FindById(id)));
IObservable <long> maxProductPrice = allOrdersProducts.Max(price => price.Price);
return(maxProductPrice.SelectMany(price => allOrdersProducts.Where(product => product.Price == price)));
}
