Action委托

.net3.5，4.0中定义了Action关键字

封装一个方法，该方法不具有参数并且不返回值。

使用此委托以参数形式传递方法，不必显式定义一个封装无参数过程的委托。

若要引用无参数并返回值的方法，请改用泛型 Func<TResult>委托。

using System; using System.Windows.Forms;
public delegate void ShowValue();
public class Name {
   private string instanceName;    public Name(string name)    {       this.instanceName = name;    }
   public void DisplayToWindow()    {       MessageBox.Show(this.instanceName);
   }
}
public class testTestDelegate {
   public static void Main()    {       Name testName = new Name("Koani");       ShowValue showMethod = testName.DisplayToWindow;
      showMethod();
   }
}

用Action委托：

public class testTestDelegate
{
   public static void Main()
   {
      Name testName = new Name("Koani");
      Action showMethod = testName.DisplayToWindow;
      showMethod();
   }
}

用Action+匿名委托

public class Anonymous
{
   public static void Main()
   {
      Name testName = new Name("Koani");
      Action showMethod = delegate() { testName.DisplayToWindow();} ;
      showMethod();
   }
}

用Action+Lambda

public class LambdaExpression
{
   public static void Main()
   {
      Name testName = new Name("Koani");
      Action showMethod = () => testName.DisplayToWindow();
      showMethod();
   }
}

那如果要传递的方法有参数怎么办，答案是用Action<T>

Action<T>有15个重载版本

同样Func<T>也有15个重载版本

View Code

    public delegate void ShowValue();
    public delegate void ShowValueName(string msg);
    public class CustomObj
    {
        public void Display()
        {
            Console.Write("hello!");
            Console.Read();
        }

        public void DisplayName(string name)
        {
            Console.Write("hello," + name);
            Console.Read();
        }

View Code

using System;
using System.Collections.Generic;
using System.Text;

namespace ActionApp
{
    class Program
    {
        static void Main(string[] args)
        {
            CustomObj obj = new CustomObj();
            //ShowValue sv = obj.Display;
            //sv();

            Action a = obj.Display;
            a();

            //Action a = delegate { obj.Display(); };
            //a();

            //Action a = () => obj.Display();
            //a();

            //ShowValueName svn = obj.DisplayName;
            //svn("dd");

            //Action<string> at = obj.DisplayName;
            //at("dd");

            //Action<string> at = delegate(string s) { obj.DisplayName(s);};
            //at("dd");

            //Action<string> at = s => obj.DisplayName(s);
            //at("dd");
        }
    }