private void AddForPreview() { if (numberOperation.Values.LastOrDefault() == elementsDictionary[btnSqrt.Content.ToString()]) { double calculateSqrt = CalculateSqrt(entryNumbers.LastOrDefault()); lblCalculation.Content += "(" + numberOperation.Values.LastOrDefault() + "(" + entryNumbers.LastOrDefault() + ")=" + calculateSqrt + ")"; lblCurrentNumber.Content = calculateSqrt; } else if (numberOperation.Values.LastOrDefault() == btnPercent.Content.ToString()) { double calculatePercent = (entryNumbers.ElementAtOrDefault(entryNumbers.Count - 2) * (entryNumbers.LastOrDefault() / 100.0d)); lblCalculation.Content += "(" + entryNumbers.ElementAtOrDefault(entryNumbers.Count - 2) + "*" + entryNumbers.LastOrDefault() + numberOperation.Values.LastOrDefault() + "=" + calculatePercent + ")"; lblCurrentNumber.Content = calculatePercent; } else { if (numberOperation.Values.ElementAtOrDefault(numberOperation.Count - 2) != elementsDictionary[btnSqrt.Content.ToString()] && numberOperation.Values.ElementAtOrDefault(numberOperation.Count - 2) != btnPercent.Content.ToString()) { lblCalculation.Content += entryNumbers.LastOrDefault() + numberOperation.Values.LastOrDefault(); lblCurrentNumber.Content = string.Empty; } else { lblCalculation.Content += numberOperation.Values.LastOrDefault(); } } }