.NET中的“闭包”是什么？ [英] What are 'closures' in .NET?

问题描述

什么是关闭？

如果它们存在于.NET中，你能否提供一个代码片段（最好是在C＃ ）解释它？

编辑：我经历了 Jon Skeet的文章来了解什么是闭包，以及如何在.NET中使用它们。

解决方案

我有一篇关于这个话题的文章。 （它有很多例子。）

实质上，闭包是一个代码块，可以在稍后的时间执行，但维护环境第一次创建 - 即使它已经完成执行，它仍然可以使用创建它的方法的局部变量等。

闭包的一般特性

这是一个使用匿名方法的示例：

using System;

class Test
{
static void Main（）
{
Action action = CreateAction（）;
action（）;
action（）;
}

static Action CreateAction（）
{
int counter = 0;
return delegate
{
//是的，它可以在一个语句中完成;
//但是它更清晰这样。
counter ++;
Console.WriteLine（counter = {0}，counter）;
};
}
}


输出：

  counter = 1 
 counter = 2 
  

$ b b

在这里我们可以看到，CreateAction返回的动作仍然可以访问计数器变量，并且确实可以增加它，即使CreateAction本身已经完成。

What is a closure? Do we have them in .NET?

If they do exist in .NET, could you please provide a code snippet (preferably in C#) explaining it?

EDIT: I went through Jon Skeet's article to understand what closures are and how to use them in .NET.

解决方案

I have an article on this very topic. (It has lots of examples.)

In essence, a closure is a block of code which can be executed at a later time, but which maintains the environment in which it was first created - i.e. it can still use the local variables etc of the method which created it, even after that method has finished executing.

The general feature of closures is implemented in C# by anonymous methods and lambda expressions.

Here's an example using an anonymous method:

using System;

class Test
{
    static void Main()
    {
        Action action = CreateAction();
        action();
        action();
    }

    static Action CreateAction()
    {
        int counter = 0;
        return delegate
        {
            // Yes, it could be done in one statement; 
            // but it is clearer like this.
            counter++;
            Console.WriteLine("counter={0}", counter);
        };
    }
}

Output:

counter=1
counter=2

Here we can see that the action returned by CreateAction still has access to the counter variable, and can indeed increment it, even though CreateAction itself has finished.

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