艾伟_转载：解惑答疑：C#委托和事件

  class Program
{
static void Main(string[] args)
    {
      　XiaoBai xiaobai = new XiaoBai();
//Google公司
        ItCompany google = new ItCompany("谷歌中国", "CTO", xiaobai);
//微软公司
        ItCompany microsoft = new ItCompany("微软中国", "架构师", xiaobai);
//花旗银行
    FinanceCompany AmericaBank = new FinanceCompany("花旗银行", "金融分析师", xiaobai);
//委托的好处，可以应用于不同的类的不同方法
//方法“委托”给委托，委托“委托”给事件
//委托类型与事件声明时的委托类型相同
//因为是传引用，所以方法后面不能带括号，带括号则是调用方法了
//一个委托可以搭载多个方法，一个事件则拥有一个委托链
        xiaobai.Update += new TheEventHandler(google.ComeToItCompany);
        xiaobai.Update += new TheEventHandler(microsoft.ComeToItCompany);
        xiaobai.Update += new TheEventHandler(AmericaBank.ComeToFinanceCompany);
        xiaobai.SubjectState = "我小白过来应聘职位啦！";
//发出通知，触发事件
        xiaobai.Notify();
//以下代码与上面相似
        XiaoHua xiaohua = new XiaoHua();
        ItCompany microsoft2 = new ItCompany("微软总公司", "CEO", xiaohua);
    FinanceCompany ChinaBank = new FinanceCompany("中国央行", "财务部总经理", xiaohua);
        xiaohua.Update += new TheEventHandler(microsoft2.ComeToItCompany);
        xiaohua.Update += new TheEventHandler(ChinaBank.ComeToFinanceCompany);
        xiaohua.SubjectState = "我小华过来应聘职位啦！";
        xiaohua.Notify()
        Console.ReadLine();
    }
}
//通知者接口
interface Subject
{
void Notify();

string SubjectState
    {
get;
set;
    }
}
 //事件处理程序的委托，相当于一个类（在编译成IL后确确实实是类）或者方法指针，
与常规类定义不同，带参数和返回值
    delegate void TheEventHandler();
//小白
class XiaoBai : Subject
{
//声明一事件Update，类型为委托TheEventHandler
    public event TheEventHandler Update;
private string action; //用Notify方法触发事件
    public void Notify()
    {
        Update();
    }
public string SubjectState
    {
get { return action; }
set { action = value; }
    }
}
//小华
class XiaoHua : Subject
{
//声明一事件Update，类型为委托TheEventHandler
    public event TheEventHandler Update;
private string action;
//用Notify方法触发事件
    public void Notify()
    {
        Update();
    }
public string SubjectState
    {
get { return action; }
set { action = value; }
    }
}
//IT行业
class ItCompany
{
private string companyname;
private string job;
private Subject sub;

public ItCompany(string _companyname, string _job, Subject _sub)
    {
        companyname = _companyname;
        job = _job;
        sub = _sub;
    }
//参数和返回值与委托TheEventHandler一致
    public void ComeToItCompany()
    {
        Console.WriteLine("{0} {1}： 来我们公司做{2}！", sub.SubjectState, 
companyname, job);
    }
}
//金融行业
class FinanceCompany
{
private string companyname;
private string job;
private Subject sub;

public FinanceCompany(string _companyname, string _job, Subject _sub)
    {
        companyname = _companyname;
        job = _job;
        sub = _sub;
    }
//参数和返回值与委托TheEventHandler一致
    public void ComeToFinanceCompany()
    {
        Console.WriteLine("{0} {1}： 来我们公司做{2}！", sub.SubjectState, 
companyname, job);
    }
}