Action＜＞是委托代理的简写形式

た入场券 2022-12-05 05:16 115阅读 0赞

# #

【Action<>】指那些只有输入参数没有返回值的委托

比如原始的委托是这样定义的：

public delegate void CommonDelegate(string param);  
    public static void Hello(string param)  
    {  
        Console.WriteLine("Good morning," + param);  
        Console.ReadLine();  
    }  
      
    CommonDelegate dAction = new CommonDelegate(Hello);  
    dAction("EveryOne");

改写为Action<>形式的委托就变成了这样：

public static void Hellow(string param)  
    {  
        Console.WriteLine("Good morning," + param);  
        Console.ReadLine();  
    }  
      
    Action<string> action = Hellow;  
    action("EveryOne");

改为lambda表达式 ：

static public  Action<string> action;
    
    action = (param) =>
    
    {
    
        Console.WriteLine("Good morning," + param);  
        Console.ReadLine();  
    
    }

从整个过程来看，省去了定义的麻烦，但是对于初学者也较难理解，一版Action<>作为回调函数使用

using System;
    using System.Collections;
     
    public class Test
    {
        static public Action A;
        static public Action<int> B;
        static public Action<int, string> C;
        static public Action<int, string, int> D;
        static public Action<int, string, int, string> E;
     
        static void Main()
        {
            A = () =>
                {
                    Console.WriteLine("I'm A ");
                };
     
            B = (i) =>
                {
                    Console.WriteLine("I'm B " + i);
                };
     
            C = (i, s) =>
                {
                    Console.WriteLine("I'm C " + i + " " + s) ;
                } ;
     
            D = (i, s, j) =>
                {
                    Console.WriteLine("I'm D " + i + " " + s + " " + j) ;
                } ;
     
            E = (i, s, j, t) =>
                {
                    Console.WriteLine("I'm E " + i + " " + s + " " + j + " " + t);
                };
     
            A();
            B(1);
            C(1, "a");
            D(1, "a", 2);
            E(1, "a", 2, "b");
                   
            Console.ReadKey();
        }
    }