public static void Put(string stringValue) { double dummy; if (double.TryParse(Calculator.value + stringValue, out dummy)) { Calculator.PutNumber(stringValue); } else if (!Calculator.isZero && Calculator.validSignals.Contains(stringValue)) { if (stringValue == "=") { Calculator.ComputeEquals(); } else if (string.IsNullOrWhiteSpace(Calculator.signal)) { Calculator.PutSignal(stringValue); } else { Calculator.ComputeEquals(); Calculator.signal = stringValue; } } }