C# 委托三种使用

不带返回值的委托

        public delegate void DelegateDemo(String s1, String s2);
        public static event DelegateDemo ddo;

        public class Test1
        {
            public void Look1(String s1, String s2)
            {
                Console.WriteLine("Look1  " + s1 + "  -1-  " + s2);
            }
            public void Look2(String s1, String s2)
            {
                Console.WriteLine("Look2  " + s1 + "  -2-  " + s2);
            }
            public void Look3(String s1, String s2)
            {
                Console.WriteLine("Look3  " + s1 + "  -3-  " + s2);
            }
        }
        

        static void Main(string[] args)
        {
            Test1 test1 = new Test1();
            //方式一 不定义事件event
            DelegateDemo dd = new DelegateDemo(test1.Look1);
            dd += new DelegateDemo(test1.Look2);
            dd += new DelegateDemo(test1.Look3);
            dd += new DelegateDemo(test1.Look3);
            dd += new DelegateDemo(test1.Look3);
            dd("111","222");
            dd("333","444");

            //方法二 先定义好事件event
            ddo += new DelegateDemo(test1.Look1);
            ddo("555","666");

            Console.ReadKey();

        }

Look1 111 -1- 222
Look2 111 -2- 222
Look3 111 -3- 222
Look3 111 -3- 222
Look3 111 -3- 222
Look1 333 -1- 444
Look2 333 -2- 444
Look3 333 -3- 444
Look3 333 -3- 444
Look3 333 -3- 444
Look1 555 -1- 666

带参数返回值的阻塞委托

//委托是一个类，它定义了方法的类型，使得可以将方法当作另一个方法的参数来进行传递，这种将方法动态地赋给参数的做法，可以避免在程序中大量使用If-Else(Switch)语句，同时使得程序具有更好的可扩展性。
//委托：具有 同样参数和返回值 的函数的集合.
        public delegate string MyDelegate(int arg, string str);
        public static string MyFunction1(int count, string str)
        {
            Debug.Print("count: "+count+"  str: "+str);
            for (int i=0;i<3;i++)
            {
                Thread.Sleep(1000 * 3);
                Debug.Print("---sleep---");
            }
            return "MyFunction1";
        }
        private void Load()
        {
            
            MyDelegate dele = new MyDelegate(MyFunction1);
            IAsyncResult res = dele.BeginInvoke(10, "abcd", null, null);
            string result = dele.EndInvoke(res);
            Debug.Print("result: "+result);

            IAsyncResult res2 = dele.BeginInvoke(20, "efgh", null, null);
            string result2 = dele.EndInvoke(res2);
            Debug.Print("result2: " + result2);

            Debug.Print("END");
        }

count: 10 str: abcd
---sleep---
---sleep---
---sleep---
result: MyFunction1
count: 20 str: efgh
---sleep---
---sleep---
---sleep---
result2: MyFunction1
END
//该方法会阻塞在EndInvoke方法

带参数返回值的非阻塞委托

public delegate string MyDelegate(int arg, string str);
        public static string MyFunction1(int count, string str)
        {
            Debug.Print("count: "+count+"  str: "+str);
            for (int i=0;i<3;i++)
            {
                Thread.Sleep(1000 * 3);
                Debug.Print("---sleep---");
            }
            return "MyFunction1";
        }
        private void Load()
        {
            MyDelegate dele = new MyDelegate(MyFunction1);
            dele.BeginInvoke(10, "abcd", CallBackFun, dele);
            Debug.Print("END");
        }

        public void CallBackFun(IAsyncResult ar)
        {
            MyDelegate caller = ar.AsyncState as MyDelegate;
            string result = caller.EndInvoke(ar);
            Debug.Print("result: " + result);
            Debug.Print("Completed!");
        }

count: 10 str: abcd
END
---sleep---
---sleep---
---sleep---
result: MyFunction1
Completed!