แจ้งเตือนผ่านอินเทอร์เฟซ

using System;
interface IChannel { void Send(string message); }
class Sms : IChannel { public void Send(string message) => Console.WriteLine($"SMS: {message}"); }
class Program
{
    static void Notify(IChannel channel, string message) => channel.Send(message);
    static void Main() => Notify(new Sms(), "Shipped");
}