public interface IService
{
    void Notif();
}

public class CustomerA : IService
{
    public void Notif()
    {
      Console.WriteLine("客户A收到通知了~~");
    }
}
public class CustomerB : IService
{
    public void Notif()
    {
      Console.WriteLine("客户B收到通知了~~");
    }
}

public class MyCompany
{
    private IList<IService> subscribers = new List<IService>();
    public void Subscribe(IService subscriber)
    {
      subscribers.Add(subscriber);
    }
    public void CancelSubscribe(IService subscriber)
    {
      subscribers.Remove(subscriber);
    }
    public void SendMsg()
    {
      foreach (IService service in subscribers)
      {
        service.Notif();
      }
    }
}

class Program
{
    static void Main(string[] args)
    {
      MyCompany company = new MyCompany();
      IService customerA = new CustomerA();
      IService customerB = new CustomerB();
      company.Subscribe(customerA);
      company.Subscribe(customerB);
      company.SendMsg();
      Console.ReadKey();
    }
}