public async Task <IEnumerable <ItemDto> > GetExchangeRatesAsync(string date)
{
if (!_dateValidationService.IsValid(date))
{
return(null);
}
var exchangeRatesRequested = await _exchangeRatesRepository.GetExchangeRatesAsync(date);
var exchangeRatesComparative =
await _exchangeRatesRepository.GetExchangeRatesAsync(_exchangeRateService.GetComparativeDate(date));
return(_exchangeRateService.GetExchangeRateChanges(exchangeRatesRequested, exchangeRatesComparative));
}