static void Main(string[] args) { string title = @" _________.__ .__ _________ .__ .__ __ / _____/|__| _____ ______ | | ____ \_ ___ \_____ | | ____ __ __| | _____ _/ |_ ___________ \_____ \ | |/ \\____ \| | _/ __ \/ \ \/\__ \ | | _/ ___\| | \ | \__ \\ __\/ _ \_ __ \ / \| | Y Y \ |_> > |_\ ___/\ \____/ __ \| |_\ \___| | / |__/ __ \| | ( <_> ) | \/ /_______ /|__|__|_| / __/|____/\___ >\______ (____ /____/\___ >____/|____(____ /__| \____/|__| \/ \/|__| \/ \/ \/ \/ \/ "; Console.WriteLine(title); Console.WriteLine("Welcome to simple calculator!"); double firstNumber = 0; double secondNumber = 0; double operationResult = 0; string operatorSymbol = ""; bool inputValid = false; string moreCalculations = ""; do { do { Console.Write("Provide first number: "); string firstInput = Console.ReadLine(); if (Double.TryParse(firstInput, out firstNumber)) { inputValid = true; } else { inputValid = false; Console.WriteLine($"{firstInput} is not a valid number!"); } } while (inputValid == false); do { Console.Write("Provide second number: "); string secondInput = Console.ReadLine(); if (Double.TryParse(secondInput, out secondNumber)) { inputValid = true; } else { inputValid = false; Console.WriteLine($"{secondInput} is not a valid number!"); } } while (inputValid == false); do { if (secondNumber == 0) { Console.Write("Provide one of the legal operators (+ OR - OR *): "); } else { Console.Write("Provide one of the legal operators (+ OR - OR / OR *): "); } string operatorInput = Console.ReadLine(); operatorSymbol = operatorInput; if (operatorInput != "+" && operatorInput != "-" && operatorInput != "/" && operatorInput != "*") { inputValid = false; Console.WriteLine($"{operatorInput} is not a valid operator!"); } else { inputValid = true; if (secondNumber == 0 && operatorInput == "/") { Console.WriteLine("Division by 0 is not allowed! Please provide different operator."); inputValid = false; } } } while (inputValid == false); operationResult = Calculator.CalculateResult(firstNumber, secondNumber, operatorSymbol); Console.WriteLine($"The result of {firstNumber} {operatorSymbol} {secondNumber} is {operationResult}"); Console.WriteLine("More calculations? (y/n): "); moreCalculations = Console.ReadLine(); } while (moreCalculations == "y"); Console.WriteLine("Bye!"); }