C# Action 委托

1.显示的 delegate

首先我们先看一个没有用Action的委托

using System;using System.Windows.Forms;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;delegate void ShowWindowsMessageDelegate(string message);namespace testDelegate{    class Program    {        public static void Main()        {            ShowWindowsMessageDelegate showWindowsMessageDelegate;            showWindowsMessageDelegate = OnShow;            showWindowsMessageDelegate("Show Windows Message Success!");        }        private static void OnShow(string message)        {            MessageBox.Show(message);        }    }}

代码 很简单, 定义了一个显示窗口的代理, 用于显示一个窗口和一段文字

2.Action<in T> 委托

using System;using System.Windows.Forms;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace testDelegate{    class Program    {        public static void Main()        {                       Action<string> ShowWindowsMessage;            ShowWindowsMessage = OnShow;            ShowWindowsMessage("Show Windows Message Success!");        }        private static void OnShow(string message)        {            MessageBox.Show(message);        }    }}

先看下Action<T>的描述

哦~~~ 原来Action<T>就是一个参数为T 的无返回值泛型委托

3.Action<in T1,in T2> 委托

那么两个参数的就自然想到了 Action<T1,T2> 

using System;using System.Windows.Forms;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;public class TestAction1{    public static void Main()    {        Action<string, int> LogMessageByTimes;        LogMessageByTimes = OnLogByTimes;        OnLogByTimes("Log By Times Success!", 3);    }    private static void OnLogByTimes(string message, int times)    {        for (int i = 0; i < times; i++)        {            Console.WriteLine(message);        }    }}

运行结果

4.ForEach 委托

using System;using System.Windows.Forms;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;class Program{    static void Main()    {        List<String> names = new List<String>();        names.Add("ForEach");        names.Add("is");        names.Add("Action<T> action");        names.Add("Actually");        // 参看ForEach 的描述 public void ForEach(Action<T> action);        // 参数 action 要对 System.Collections.Generic.List<T> 的每个元素执行的 System.Action<T> 委托。        // 所以 names.ForEach(Print); 这句代码其实也是使用的 Action<T> delegate        names.ForEach(Print);    }    private static void Print(string s)    {        Console.WriteLine(s);    }}

5.匿名方法作为委托参数

using System;using System.Windows.Forms;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;public class TestAnonMethod{    public static void Main()    {        Action<string> ShowWindowsMessage;        ShowWindowsMessage = delegate(string s) { OnShow(s); };        ShowWindowsMessage("Show Windows Message Success!");    }    private static void OnShow(string message)    {        MessageBox.Show(message);    }}