Expenses.CurrencyProviders.ECBCurrencyProvider.GetRate C# (CSharp) Méthode

        private decimal GetRate(XDocument doc, string isoCode)
        {
            var ns = doc.Root.GetDefaultNamespace();
            var rates = doc.Descendants(ns + "Cube");
            
            var rate = rates.FirstOrDefault(r =>
            {
                if (r.HasAttributes)
                {
                    var currency = r.Attribute("currency");
                    if (currency != null && currency.Value.ToUpper() == isoCode)
                        return true;
                }
                return false;
            });

            if (rate == null)
                throw new Exception("Unable to find requested rate in ECB: " + isoCode);

            return decimal.Parse(rate.Attribute("rate").Value);
        }
    }