public static void DoMethod(int a, int b) { int caseSwitch; do { Console.WriteLine(); Console.WriteLine("Select a mathematical operation:"); Console.WriteLine("1 -> (+); 2 -> (-); 3 -> (*); 4 -> (/)"); Console.WriteLine("Write (0) to close programm"); caseSwitch = Convert.ToInt32(Console.ReadLine()); switch (caseSwitch) { case 1: Console.WriteLine("a + b = " + MathMethods.Summ(a, b)); break; case 2: Console.WriteLine("a - b = " + MathMethods.Diff(a, b)); break; case 3: Console.WriteLine("a * b = " + MathMethods.Multiplication(a, b)); break; case 4: Console.WriteLine("a / b = " + MathMethods.Division(a, b)); break; case 0: break; default: Console.WriteLine("Operation does't exist"); break; } } while (caseSwitch != 0); }