calculator.C#

using System;

namespace CalculatorApp
{
    class MainClass
    {
        public static int firstNumber;
        public static int secondNumber;
        public static int result;

       
       
       public static void Main(string[] args)
        {
            string userChoice;
            do
            {
                Console.Clear();
                string operatorSign;
                Console.WriteLine("Enter an operation sign");
                operatorSign = Console.ReadLine();
                while (true)
                {
                    if (operatorSign.Equals("+")) 
                    {
                        Prompt("+");
                    } 

                    else if (operatorSign.Equals("*"))
                    {
                        Prompt("*");
                    }

                    else if (operatorSign.Equals("-"))
                    {
                        Prompt("-");
                    }

                    else if (operatorSign.Equals("/"))
                    {
                        Prompt("/");
                    }

                    else if (operatorSign.Equals("%"))
                    {
                        Prompt("%");
                    }

                    else
                    {
                        Console.WriteLine("Wrong input");
                    }
                    break;
                }
                //Console.WriteLine(firstNumber);
                Console.WriteLine("Type yes to restart");
                userChoice = Console.ReadLine();
            } while (userChoice == "yes");

        }

        public static void Prompt(string sign)
        {
            Console.WriteLine("Enter first number");
            string num1 = Console.ReadLine();
            bool isTrueNUm1 = Int32.TryParse(num1, out int value1);

            while(true)
            {
                if (isTrueNUm1)
                {
                    firstNumber = value1;
                }
                else
                {
                    Console.WriteLine("Wrong input");
                }
                break;
            }

            if (isTrueNUm1)
            {
                Console.WriteLine("Enter second number");
                string num2 = Console.ReadLine();
                bool isTrueNUm2 = Int32.TryParse(num2, out int value2);

                /*if number one is wrong input, no chance for 
                 * inputing number two.We just restart */
                
                    while (true)
                    {

                    if (isTrueNUm2)
                    {
                        secondNumber = value2;
                    }
                    else
                    {
                        Console.WriteLine("Wrong input");
                    }
                    break;
                }
            }


            switch (sign)
                    {
                        case "*":
                            result = firstNumber * secondNumber;
                            Console.WriteLine("The answer is: " + result);
                            break;

                        case "+":
                            result = firstNumber + secondNumber;
                            Console.WriteLine("The answer is: " + result);
                            break;

                        case "-":
                            result = firstNumber - secondNumber;
                            Console.WriteLine("The answer is: " + result);
                            break;

                        case "/":
                            result = firstNumber / secondNumber;
                            Console.WriteLine("The answer is: " + result);
                            break;
                        
                        case "%":
                            result = firstNumber % secondNumber;
                            Console.WriteLine("The answer is: " + result);
                            break;
                        default:
                            Console.WriteLine("Wrong input");
                            break;
                    }
                }
            }
        }