using System;

​

public class Calculator

{

    public static double DoOperation(double num1, double num2, string op)

    {

        double result = double.NaN;

        switch (op)

        {

             case "a":

                result = num1 + num2;

                break;

            case "s":

                result = num1 - num2;

                break;

             case "m":

                result = num1 * num2;

                break;

            case "d":

                if (num2 != 0)

                {

                    result = num1 / num2;

                }

                break;

            default:

                break;

        }

        return result;

    }

}

​

public class Program

{

    public static void Main()

    {

        bool endApp = false;

        Console.WriteLine("Console Calculator in C#\r");

        Console.WriteLine("------------------------\n");

        while (!endApp)

        {

            string numInput1 = "";

            string numInput2 = "";

            double result = 0;

            Console.Write("Type a number, and then press Enter: ");

            numInput1 = Console.ReadLine();

​

            double cleanNum1 = 0;

            while (!double.TryParse(numInput1, out cleanNum1))

            {

                Console.Write("This is not valid input. Please enter an integer value: ");

                numInput1 = Console.ReadLine();

            }

            Console.Write("Type another number, and then press Enter: ");

            numInput2 = Console.ReadLine();

​

            double cleanNum2 = 0;

            while (!double.TryParse(numInput2, out cleanNum2))

            {

                Console.Write("This is not valid input. Please enter an integer value: ");

                numInput2 = Console.ReadLine();

            }

            Console.WriteLine("Choose an operator from the following list:");

            Console.WriteLine("\ta - Add");

            Console.WriteLine("\ts - Subtract");

            Console.WriteLine("\tm - Multiply");

            Console.WriteLine("\td - Divide");

            Console.Write("Your option? ");

            string op = Console.ReadLine();

            try

            {

                result = Calculator.DoOperation(cleanNum1, cleanNum2, op);

                if (double.IsNaN(result))

                {

                    Console.WriteLine("This operation will result in a mathematical error.\n");

                }

                else Console.WriteLine("Your result: {0:0.##}\n", result);

            }

            catch (Exception e)

            {

                Console.WriteLine("Error...\n - Details: " + e.Message);

            }

            Console.WriteLine("------------------------\n");

            Console.Write("Press 'n' and Enter to close the app, or press any other key and Enter to continue: ");

            if (Console.ReadLine() == "n") endApp = true;

​

            Console.WriteLine("\n"); 

        }

        return;

    }

}

​

​

​