static void Main(string[] args) { double input = 0; var calc = Operator.GetInstance(); while (input != 99) { Console.WriteLine("Choose Operator:\n1.Add\n2.Subtract\n3.Multiply\n4.Divide\n5.Quit"); input = Convert.ToDouble(Console.ReadLine()); //Console.WriteLine(input); //Add if (input == 1) { Console.WriteLine("First Number: "); double num1 = Convert.ToDouble(Console.ReadLine()); Console.WriteLine("Second Number: "); double num2 = Convert.ToDouble(Console.ReadLine()); Console.WriteLine("Sum: " + calc.Add(num1, num2) + "\n"); } //Subtract else if (input == 2) { Console.WriteLine("First Number: "); double num1 = Convert.ToDouble(Console.ReadLine()); Console.WriteLine("Second Number: "); double num2 = Convert.ToDouble(Console.ReadLine()); Console.WriteLine("Answer: " + calc.Subtract(num1, num2) + "\n"); } //Multiply else if (input == 3) { Console.WriteLine("First Number: "); double num1 = Convert.ToDouble(Console.ReadLine()); Console.WriteLine("Second Number: "); double num2 = Convert.ToDouble(Console.ReadLine()); Console.WriteLine("Answer: " + calc.Multiply(num1, num2) + "\n"); } //Divide else if (input == 4) { Console.WriteLine("First Number: "); double num1 = Convert.ToDouble(Console.ReadLine()); Console.WriteLine("Second Number: "); double num2 = Convert.ToDouble(Console.ReadLine()); Console.WriteLine("Answer: " + calc.Divide(num1, num2) + "\n"); } //Quit else if (input == 5) { input = 99; } else { Console.WriteLine("Not an Option. Try Again!\n"); } } }