[C#1] 10-事件

 1 class RingManager
 2 {
 3     /*
 4     * 定义一个类型保存发送给事件登记者的附加信息，
 5     * 按照.NET框架的约定，所有这样保存事件信息的类型
 6     * 都继承自System.EventArgs,且以EventArgs作
 7     * 为名字的结尾。    
 8     */
 9     public class SchoolBellEventArgs : EventArgs
10     {
11         //教室位置
12         public readonly string classRoom;
13         //上课时间
14         public readonly DateTime schoolTime;
15  
16         public SchoolBellEventArgs(string classroom,
17             DateTime schooltime)
18         {
19             this.classRoom = classroom;
20             this.schoolTime = schooltime;
21         }
22     }
23  
24     /* 按照.NET框架的约定，委托类型的名称应该以
25     * EventHander结束，回调方法的 原型有一个void返回值
26     * 并且接受两个参数【object指向发送通知的对象，
27     * e是给接受者的附加信息】
28     */
29     public delegate void SchoolBellEventHandler
30         (object sender, SchoolBellEventArgs e);
31  
32     //声明事件成员
33     public event SchoolBellEventHandler SchoolBell;
34  
35     //负责通知事件的登记对象
36     public void OnSchoolBell(SchoolBellEventArgs e)
37     {
38         if (SchoolBell != null)
39         {
40             SchoolBell(this, e);
41         }
42     }
43     //把输入的参数转化为事件调用
44     public void IsOnTimeToClass(string classRoom,
45         DateTime time)
46     {
47         OnSchoolBell(new SchoolBellEventArgs
48             (classRoom, time));
49     }
50 }

public event SchoolBellEventHandler SchoolBell;

 1 public event SchoolBellEventHandler SchoolBell
 2  //虽然我们声明的是public，但是编译器为我们产生了private的 私有字段
 3  //这样做可以防止类型外的的错误操作[也说明事件在一方面封装了委托]
 4  .field private class RingManager/SchoolBellEventHandler SchoolBell
 5 
 6  //add_SchoolBell方法注册事件
 7  .method public hidebysig specialname instance void
 8     add_SchoolBell(class RingManager/SchoolBellEventHandler
 9     'value') cil managed synchronized
10  {
11     //......省略
12     //调用System.Delegate的静态方法Combine把委托对象添加到委托链表
13     IL_0008: call class[mscorlib]System.Delegate[mscorlib]System.Delegate::
14         Combine(class [mscorlib]System.Delegate, class [mscorlib]System.Delegate)
15     //..省略
16  }
17 
18  //注销事件
19  .method public hidebysig specialname instance void
20     remove_SchoolBell(class RingManager/SchoolBellEventHandler
21     'value') cil managed synchronized
22  {
23     //。。。省略
24     //调用System.Delegate的静态方法Remove从委托链表中移除委托对象
25     IL_0008:callclass[mscorlib]System.Delegate[mscorlib]System.Delegate::
26         Remove(class [mscorlib]System.Delegate,class [mscorlib]System.Delegate)
27  //。。。省略
28  }

.event RingManager/SchoolBellEventHandler SchoolBell
{
    .addon instance void RingManager::add_SchoolBell(class RingManager/SchoolBellEventHandler)
    .removeon instance void RingManager::remove_SchoolBell(class RingManager/SchoolBellEventHandler)
} // end of event RingManager::SchoolBell

 1 //老师类，学生类就不写了
 2 class Teacher
 3 {
 4     //构造老师对象时穿进去RingManager
 5     public Teacher(RingManager rm)
 6     {
 7         rm.SchoolBell += 
 8             new RingManager.SchoolBellEventHandler(rm_SchoolBell);
 9     }
10  
11     //老师的回调方法
12     private void rm_SchoolBell(object sender, 
13         RingManager.SchoolBellEventArgs e)
14     {
15         //sender表示RingManager的对象
16         Console.WriteLine("上课铃响了--我是老师：");
17         //e是事件的附加信息
18         Console.WriteLine("在{0}上课,现在时间是{1}",
19             e.classRoom, e.schoolTime);
20     }
21  
22     //注销SchoolBell事件
23     public void UnRegister(RingManager rm)
24     {
25         RingManager.SchoolBellEventHandler rm_sbea =
26             new RingManager.SchoolBellEventHandler(rm_SchoolBell);
27         rm.SchoolBell -= rm_sbea;
28     }
29 }

static void Main()
{
    RingManager rm = new RingManager();
    Teacher t = new Teacher(rm);
    //触发事件，老师t的到通知，做他该做的事情
    rm.IsOnTimeToClass("教学楼320教室", DateTime.Now);
    //老师注销该事件
    t.UnRegister(rm);
    //再次触发事件，这次老师t接受不到通知了
    rm.IsOnTimeToClass("教学楼320教室", DateTime.Now);
}

 1 //声明一个私有的委托字段
 2 private SchoolBellEventHandler _SchoolBell;
 3  
 4 //像是属性一样的写法，add和remove都接受一个隐含参数value
 5 public event SchoolBellEventHandler SchoolBell
 6 {
 7     add
 8     {
 9         //添加value（委托对象）到委托链表
10         _SchoolBell = (SchoolBellEventHandler)
11             Delegate.Combine(_SchoolBell, value);
12     }
13     remove
14     {
15         //从委托链表_SchoolBell中移除value（委托对象）
16         _SchoolBell = (SchoolBellEventHandler)
17             Delegate.Remove(_SchoolBell, value);
18     }
19 }
20  
21 //负责通知事件的登记对象
22 public void OnSchoolBell(SchoolBellEventArgs e)
23 {
24     if (_SchoolBell != null)
25     {
26         _SchoolBell(this, e);
27     }
28 }