委托和lambda

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DelegatesAndLambda
{
    //委托:定义了方法的类型，存储是一些具有相同签名(相同返回值、相同参数)的方法的地址列表
    //泛型委托:委托重用
    //lambda:本质来说是一个匿名方法
    class Program
    {
        //自定义委托
        delegate void hellodelegate(string msg);

        //泛型委托
        delegate void genericsDelegate<T>(T a);

        static void Main(string[] args)
        {
            //初始化
            hellodelegate hello = new hellodelegate(SayHelloByEglish);
            genericsDelegate<string> gdl = new genericsDelegate<string>(SayHelloByEglish);
            genericsDelegate<int> gdl2 = new genericsDelegate<int>(AddNum);
            //预定义委托
            //无返回值
            Action<string> action = new Action<string>(SayHelloByEglish);
            action("Speak English");
            //有返回值 TResult 返回值泛型
            Func<string,string> func = new Func<string,string>(SayHelloToWorld);
            Console.WriteLine(func("有返回值的预定义委托"));

            //labmda表达式
            //使用匿名方法
            Action<string> action1 = new Action<string>(delegate (string msg) {
                Console.WriteLine(msg);
            });
            Action<string> action2 = new Action<string>((string msg) => {
                Console.WriteLine(msg);
            });
            //一个参数 一个语句
            Action<string> action3 = new Action<string>( msg => {
                Console.WriteLine(msg);
            });
            //无参无返回值
            Action action4 = new Action(() => {
                Console.WriteLine("");
            });
            //调用
            hello.Invoke("My Speck English");
            gdl("Say japanese");
            gdl2(5);
            action1("匿名委托");
            Console.ReadKey();
        }

        public static void SayHelloByEglish(string msg)
        {
            Console.WriteLine(msg);
        }

        public static void AddNum(int a)
        {
            Console.WriteLine(a + 5);
        }

        public static string SayHelloToWorld(string param)
        {
            return param;
        }
    }

}