private void UpdatePreviousRate(Rate previousRate, double buy, double sell)
 {
     _localSettings.UpdateSetting(previousRate.Name, EnumHandler.GetDescriptionFromEnumValue(RateOptions.Buy), buy.ToString());
     _localSettings.UpdateSetting(previousRate.Name, EnumHandler.GetDescriptionFromEnumValue(RateOptions.Sell), sell.ToString());
     _localSettings.UpdateSetting(previousRate.Name, "date", DateTime.Now.ToString());
 }