C#中的事件(event)处理机制

1 [访问修饰符] delegate 返回类型 委托名();

 1 //定义委托
 2 public delegate int Callback(int num1, int num2);
 3 //定义方法类
 4 class MathCalc{
 5     //加法方法
 6     public int Plus(int number1, int number2){
 7         return number1 + number2;
 8     }
 9 }
10 
11 static void Main(string[] args){
12     //委托的对象
13     Callback objCall;
14     //实例MathCalc类的对象
15     MathCalc mc = new MathCalc();
16     //将方法与委托关联起来
17     objCall = new Callback(mc.Plus);
18     //可以用Callback objCall = new Callback(mc.Plus);声明委托并与方法关联
19     //将委托实例化
20     int result = objCall(1, 2);
21     System.Console.WriteLine("结果为{0}", result);
22 }

1 委托类型 委托实例 = delegate([参数列表]) { 
2 　　//代码块 
3 }; //分号不能少

 1 class Program{
 2     //定义委托
 3     delegate int delSum(int num1, int num2);
 4     static void Main(string[] args){
 5         int third = 3;
 6         //将代码传递为委托参数
 7         delSum deladd = delegate(int first, int second){
 8             int sum = first + second;
 9             return sum;
10         };
11         int total = deladd(1, 2) + third;
12         Console.WriteLine("1+2+3="+total);
13     }
14 }

 1 public class MeltdownEventArgs : EventArgs {
 2     private string message;
 3     public MeltdownEventArgs(string message) {
 4         this.message = message;
 5     }
 6     public string Message {
 7         get {
 8             return message;
 9         }
10     }
11 }
12 
13 public class Reactor {
14     private int temperature;
15     //定义委托
16     public delegate void MeltdownHandler(object reactor, MeltdownEventArgs MEA);
17     //定义事件
18     public event MeltdownHandler OnMeltdown;
19     public int Temperature {
20         set {
21             temperature = value;
22             //当温度值高于1000时，创建叫myMEA的MeltdownEventArgs对象，并把字符串传递进来给myMEA的message属性，然后产生OnMeltdown事件，把当前的Reactor对象和myMEA作为参数传递给OnMeltdown
23             if (temperature > 1000){
24                 MeltdownEventArgs myMEA = new MeltdownEventArgs("Reactor meltdown in progress!");
25                 OnMeltdown(this, myMEA);
26             }
27         }
28     }
29 }
30 
31 public class ReactorMonitor {
32     //ReactorMonitor构造函数接收Reactor对象myReactor为参数
33     public ReactorMonitor(Reactor myReactor) {
34         //该构造函数为OnMeltdown事件监视myReactor对象。当myReactor对象产生OnMeltdown事件时，DisplayMessage()方法会被调用来处理这个事件
35         myReactor.OnMeltdown += new Reactor.MeltdownHandler(DisplayMessage);
36     }
37     public void DisplayMessage(object myReactor, MeltdownEventArgs myMEA) {
38         Console.WriteLine(myMEA.Message);
39     }
40 }
41 
42 public static void Main(string[] args) {
43     Reactor myReactor = new Reactor();
44     ReactorMonitor myReactorMonitor = new ReactorMonitor(myReactor);
45 
46     Console.WriteLine("Setting reactor temperature to 100 degrees Centigrade");
47     //设置温度值为100
48     myReactor.Temperature = 100;
49     Console.WriteLine("Setting reactor temperature to 2000 degrees Centigrade");
50     //设置温度值为2000
51     myReactor.Temperature = 2000;
52 }