static void Main() { Console.WriteLine("Input a number"); int number = Convert.ToInt32(Console.ReadLine()); Console.WriteLine("Input a second number (optional)"); string input = Console.ReadLine(); MathOperations math = new MathOperations(); if (input != "") { int number2 = Convert.ToInt32(input); Console.WriteLine(math.Add(number, number2)); } else { Console.WriteLine(math.Add(number)); } Console.Read(); }