:P

using System;
namespace Program
{
    class Program
    {
        static void Main(string[] args)
        {
            string choice;
            double numberOne;
            bool resultOne;
            do
            {
                Console.Write("Enter A:");
                resultOne = Double.TryParse(Console.ReadLine(), out numberOne);
            }
            while (!resultOne);
            double numberTwo;
            bool resultTwo;
            do
            {
                Console.Write("Enter B:");
                resultTwo = Double.TryParse(Console.ReadLine(), out numberTwo);
            }
            while (!resultTwo);
            do
            {
                Console.WriteLine("Methods: +, -, *, /, %");
                Console.Write("Choose method:");
                string method = Console.ReadLine();
                if (method == "+")
                {
                    Console.WriteLine("Addition:" + (numberOne + numberTwo));
                }
                else if (method == "-")
                {
                    Console.WriteLine("Substraction:" + (numberOne - numberTwo));
                }
                else if (method == "*")
                {
                    Console.WriteLine("Multiplication:" + (numberOne * numberTwo));
                }
                else if (method == "/")
                {
                    Console.WriteLine("Division:" + (numberOne / numberTwo));
                }
                else if (method == "%")
                {
                    Console.WriteLine("Modulus:" + (numberOne % numberTwo));
                }
                else
                    Console.WriteLine("Not existing method. Error 404.");
                Console.WriteLine("To continue choose different method.");
                Console.WriteLine("To quit type exit.");
                choice = Console.ReadLine();
            }
                while(!choice.Equals("exit"));
            {
            }
        }
    }
    }