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<bool> 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<bool> 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 Func<T, TResult> 委托。
using System; using System.IO; public class Anonymous { public static void Main() { OutputTarget output = new OutputTarget(); Func<bool> 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(); } }
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时间: 2024-10-13 09:24:59