事件

事件基于委托，为委托提供了一种发布/订阅机制。

public class CarInfoEventArgs:EventArgs
{
    public CarInfoEventArgs(string car)
    {
        this.Car = car;
    }
    public string Car { get; set; }
}

public class CarDealer
{
    public event EventHandler<CarInfoEventArgs> NewCarInfo;

    public void NewCar(string car)
    {
        Console.WriteLine("CarDealer, new car  {0}",car);
        RaiseNewCarInfo(car);
    }

    public virtual void RaiseNewCarInfo(string car)
    {
        EventHandler<CarInfoEventArgs> newCarInfo = NewCarInfo;
        if(newCarInfo!=null)
        {
            newCarInfo(this,new CarInfoEventArgs(car));
        }
    }
}

public class Consumer
{
    private string name;

    public Consumer(string name)
    {
        this.name = name;
    }

    public void NewCarIsHere(object sender,CarInfoEventArgs e)
    {
        Console.WriteLine("{0} : car {1} is new ",name,e.Car );
    }
}

    static void Main()
    {
      var dealer = new CarDealer();

        var michael = new Consumer("michael");
        dealer.NewCarInfo += michael.NewCarIsHere;

        dealer.NewCar("Ferrari");

        var zhangsan = new Consumer("zhangsan");
        dealer.NewCarInfo += zhangsan.NewCarIsHere;

        dealer.NewCar("lisi");

        dealer.NewCarInfo -= michael.NewCarIsHere;
        dealer.NewCar("Red Bull Racing");
        Console.ReadKey();
    }