using System;

/*
 * пишем калькулятор C#
 */
class Program
{
    static void Main()
    {
        while (true)
        {
            Console.Clear();
            double a, b, result;
            string action;
            try
            {
                //if else
                Console.WriteLine(value: "Введите первое число");
                a = double.Parse(Console.ReadLine());
                Console.WriteLine(value: "Введите первое число");
                b = double.Parse(Console.ReadLine());
                Console.WriteLine(value: "Действие + - % * /");
                action = Console.ReadLine();
                result = 0;

                if (action == "+")
                {
                    result = a + b;
                }
                else if (action == "-")
                {
                    result = a - b;
                }
                else if (action == "%")
                {
                    result = a % b;
                }
                else if (action == "*")
                {
                    result = a * b;
                }
                else if (action == "/")
                {
                    if (b == 0)
                        result = 0;
                    else
                        result = a / b;
                }
                else
                {
                    Console.WriteLine(Environment.NewLine + "Я не знаю!");
                }
                Console.WriteLine("Результат if else: " + result);

                //switch
                Console.WriteLine(Environment.NewLine + "Введите действие + - * % /" + Environment.NewLine);

                ConsoleKey consoleKey = Console.ReadKey().Key;
                switch (consoleKey)
                {
                    case ConsoleKey.Add:
                    case ConsoleKey.OemPlus:
                        result = a + b;
                        break;
                    case ConsoleKey.Subtract:
                    case ConsoleKey.OemMinus:
                        result = a - b;
                        break;
                    case ConsoleKey.Multiply:
                        result = a * b;
                        break;
                    case ConsoleKey.Divide:
                        if (b == 0)
                            result = 0;
                        else
                            result = a / b;
                        break;
                    case ConsoleKey.D5:
                        result = a % b;
                        break;
                    default:
                        Console.WriteLine(Environment.NewLine + "Я не знаю!");
                        break;
                }

                Console.WriteLine(Environment.NewLine + "Результат switch: " + result);
            }
            catch (Exception)
            {
                Console.WriteLine("Ошибка!");
                continue;
            }

            Console.ReadLine();
        }
    }
}