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

    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();

        }

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");
        }
    }