static void Main(string[] args) { Addition a = new Addition(); Substraction s = new Substraction(); Calculator c = new Calculator(a); Console.WriteLine(c.doaction(10, 15)); Console.ReadKey(); Calculator c1 = new Calculator(s); Console.WriteLine(c1.doaction(10, 15)); Console.ReadKey(); Calculator2 c2 = new Calculator2(); c2.operation = a; Console.WriteLine(c2.doaction(20, 4)); Console.ReadKey(); c2.operation = s; Console.WriteLine(c2.doaction(16, 11)); Console.ReadKey(); }