委托的高级使用

1. 多播委托（multicast）一个委托里面包含了不止一个方法

   static void Main(string[] args)
           {
               Student stu1 = new Student() { ID=1,PenColor=ConsoleColor.Yellow};
               Student stu2 = new Student { ID = 2, PenColor = ConsoleColor.Green };
               Student stu3 = new Student { ID = 3, PenColor = ConsoleColor.Red };
   
               Action action1 = new Action(stu1.DoHomeWork);
               Action action2 = new Action(stu2.DoHomeWork);
               Action action3 = new Action(stu3.DoHomeWork);
               action1 += action2;
               action1 += action3;
               action1();//多播委托，根据封装方法的顺序
               //action1();//单播委托
               //action2();//单播委托
               //action3();//单播委托
               Console.ReadLine();
           }
       }
       class Student
       {
           public int ID { get; set; }
           public ConsoleColor PenColor { get; set; }
           public void DoHomeWork()
           { 
           for(int i=0;i<5;i++)
           {
               Console.ForegroundColor = this.PenColor;
               Console.WriteLine("Student{0} doing homework {1} hours",this.ID,i);
               Thread.Sleep(1000);
           }
           }
       }

   2.隐式异步调用

• 同步和异步的语言差别，在英语中异步是两个人同时做，同步是我在你的基础上做
• 同步调用与异步调用的对比
  • 每个程序都是一个进程（process）
  • 每个进程可以有一个或者多个线程（thread）
  • 同步调用时在一个线程内
  • 异步调用的底层机理是多线程(多线程同时访问资源时，要注意线程之间争夺资源的冲突，这个时候要为线程加锁)
  • 串行=同步=单线程，并行=异步=多线程

 class Program
    {
        static void Main(string[] args)
        {
            Student stu1 = new Student() { ID=1,PenColor=ConsoleColor.Yellow};
            Student stu2 = new Student { ID = 2, PenColor = ConsoleColor.Green };
            Student stu3 = new Student { ID = 3, PenColor = ConsoleColor.Red };

            //stu1.DoHomeWork();//直接调用，同步
            //stu2.DoHomeWork();
            //stu3.DoHomeWork();

            Action action1 = new Action(stu1.DoHomeWork);//间接调用，同步
            Action action2 = new Action(stu2.DoHomeWork);
            Action action3 = new Action(stu3.DoHomeWork);
            //action1 += action2;
            //action1 += action3;
            //action1();//多播委托，根据封装方法的顺序//间接调用，同步


            //action1();//单播委托//间接调用，同步
            //action2();//单播委托
            //action3();//单播委托


            //委托的异步调用
            //action1.BeginInvoke(null,null);//隐式间接的异步调用，会生成一个分支方法，两个参数第一个参数是回调方法，只子线程执行完，需要执行什么东西
            //action2.BeginInvoke(null, null);//
            //action3.BeginInvoke(null, null);



         //一般的多线程
            Thread thread1 = new Thread(new ThreadStart(stu1.DoHomeWork));//显式的直接的异步调用，
            Thread thread2 = new Thread(new ThreadStart(stu2.DoHomeWork));
            Thread thread3 = new Thread(new ThreadStart(stu3.DoHomeWork));

            thread1.Start();
            thread2.Start();
            thread3.Start();

            //高级一点带委托的多线程
            Task task1 = new Task(new Action(stu1.DoHomeWork));//显式的异步调用
            Task task2 = new Task(new Action(stu2.DoHomeWork));
            Task task3 = new Task(new Action(stu3.DoHomeWork));

            task1.Start();
            task2.Start();
            task3.Start();


            for (int i = 0; i < 10;i++ )
            {
                Console.ForegroundColor = ConsoleColor.Cyan;
                Console.WriteLine("Main thread{0}",i);
                Thread.Sleep(1000);
            }
                Console.ReadLine();
        }
    }
    class Student
    {
        public int ID { get; set; }
        public ConsoleColor PenColor { get; set; }
        public void DoHomeWork()
        { 
        for(int i=0;i<5;i++)
        {
            Console.ForegroundColor = this.PenColor;
            Console.WriteLine("Student{0} doing homework {1} hours",this.ID,i);
            Thread.Sleep(1000);
            
        }
        }
    }

应当适时使用接口取代对委托的使用

• java完全使用接口取代了委托的功能，java没有与C#中委托相对应的实体
• 重构代码一般是指把代码放在更合适的地方