继上篇EventHandler之后，继续填坑，简单了解下Func<TResult> 委托 和 Action 委托.

msdn对于两者的解释：

Func<TResult>：封装一个不具有参数但却返回 TResult 参数指定的类型值的方法。

Action：封装一个方法，该方法不具有参数并且不返回值。

 

两者的区别在于：有无返回值。

至于 Func<T,TResult>、Func<T1,T2,TResult>....

       Action<T>、Action<T1, T2>.... ，就是参数个数的区别了 。

 

借用msdn上面的例子来说明两者的使用方式：

Func<TResult>:

using System;using System.IO;public class TestDelegate{   public static void Main()   {      OutputTarget output = new OutputTarget();      Func
     
       methodCall = output.SendToFile;      if (methodCall())         Console.WriteLine("Success!");       else         Console.WriteLine("File write operation failed.");   }}public class OutputTarget{   public bool SendToFile()   {      try      {         string fn = Path.GetTempFileName();         StreamWriter sw = new StreamWriter(fn);         sw.WriteLine("Hello, World!");         sw.Close();         return true;      }        catch      {         return false;      }   }}
     

您可以按照以下示例所演示的那样在 C# 中将 Func<TResult> 委托与匿名方法一起使用。

using System;using System.IO;public class Anonymous{   public static void Main()   {      OutputTarget output = new OutputTarget();      Func
     
       methodCall = delegate() { return output.SendToFile(); };      if (methodCall())         Console.WriteLine("Success!");       else         Console.WriteLine("File write operation failed.");   }}public class OutputTarget{   public bool SendToFile()   {      try      {         string fn = Path.GetTempFileName();         StreamWriter sw = new StreamWriter(fn);         sw.WriteLine("Hello, World!");         sw.Close();         return true;      }        catch      {         return false;      }   }}
     

　　您也可以按照以下示例所演示的那样将 lambda 表达式分配给  委托。

using System;using System.IO;public class Anonymous{   public static void Main()   {      OutputTarget output = new OutputTarget();      Func
     
       methodCall = () => output.SendToFile();       if (methodCall())         Console.WriteLine("Success!");       else         Console.WriteLine("File write operation failed.");   }}public class OutputTarget{   public bool SendToFile()   {      try      {         string fn = Path.GetTempFileName();         StreamWriter sw = new StreamWriter(fn);         sw.WriteLine("Hello, World!");         sw.Close();         return true;      }        catch      {         return false;      }   }}
     

　　

 

再来看 Action<> 的使用：

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

您也可以按照以下示例所演示的那样在 C# 中将 Action 委托与匿名方法一起使用。

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

您也可以按照以下示例所演示的那样将 lambda 表达式分配给 Action 委托实例。

using System;using System.Windows.Forms;public class Name{   private string instanceName;   public Name(string name)   {      this.instanceName = name;   }   public void DisplayToConsole()   {      Console.WriteLine(this.instanceName);   }   public void DisplayToWindow()   {      MessageBox.Show(this.instanceName);   }}public class LambdaExpression{   public static void Main()   {      Name testName = new Name("Koani");      Action showMethod = () => testName.DisplayToWindow();      showMethod();   }}

 

慢慢积累，加油