public decimal GetRate(Currency currFrom, Currency currTo) { if (currFrom == currTo) { return(1m); } TimeSpan difference = DateTime.Now - _updateTime; if (difference >= _updateDifference) { UpdateRate(currFrom); } foreach (Rate c in _rates) { if (c.Curr1 == currFrom && c.Curr2 == currTo) { return(c.Coefficient); } } throw new InvalidOperationException(ExceptionMessages.ExchangeRatesNoFittedRate()); }