闭包中变量捕获的详细说明

1. 是棘手的。一分钟内就会出现。
2. 没什么区别-在两种情况下，捕获的都是变量本身。
3. 不，没有拳击发生。

通过示例演示捕获的工作方式可能是最简单的…

这是一些使用lambda表达式捕获单个变量的代码：

using System;class Test{    static void Main()    {        Action action = CreateShowAndIncrementAction();        action();        action();    }    static Action CreateShowAndIncrementAction()    {        Random rng = new Random();        int counter = rng.Next(10);        Console.WriteLine("Initial value for counter: {0}", counter);        return () =>        { Console.WriteLine(counter); counter++;        };    }}

现在，这就是编译器为您执行的操作-只是它将使用“无法说”的名称，而这在C＃中是不可能真正出现的。

using System;class Test{    static void Main()    {        Action action = CreateShowAndIncrementAction();        action();        action();    }    static Action CreateShowAndIncrementAction()    {        ActionHelper helper = new ActionHelper();     Random rng = new Random();        helper.counter = rng.Next(10);        Console.WriteLine("Initial value for counter: {0}", helper.counter);        // Converts method group to a delegate, whose target will be a        // reference to the instance of ActionHelper        return helper.DoAction;    }    class ActionHelper    {        // Just for simplicity, make it public. I don't know if the        // C# compiler really does.        public int counter;        public void DoAction()        { Console.WriteLine(counter); counter++;        }    }}

如果捕获在循环中声明的变量，那么

ActionHelper

当您捕获来自不同作用域的变量时，它会变得更加复杂…让我知道您是否真的想要那种详细程度，或者您可以编写一些代码，在Reflector中反编译然后按照以下步骤进行:)

注意如何：

• 没有拳击
• 没有涉及指针或任何其他不安全的代码

编辑：这是两个代表共享变量的示例。一个代表显示的当前值

counter

using System;class Program{    static void Main(string[] args)    {        var tuple = CreateShowAndIncrementActions();        var show = tuple.Item1;        var increment = tuple.Item2;        show(); // Prints 0        show(); // Still prints 0        increment();        show(); // Now prints 1    }    static Tuple<Action, Action> CreateShowAndIncrementActions()    {        int counter = 0;        Action show = () => { Console.WriteLine(counter); };        Action increment = () => { counter++; };        return Tuple.Create(show, increment);    }}

…以及扩展：

using System;class Program{    static void Main(string[] args)    {        var tuple = CreateShowAndIncrementActions();        var show = tuple.Item1;        var increment = tuple.Item2;        show(); // Prints 0        show(); // Still prints 0        increment();        show(); // Now prints 1    }    static Tuple<Action, Action> CreateShowAndIncrementActions()    {        ActionHelper helper = new ActionHelper();        helper.counter = 0;        Action show = helper.Show;        Action increment = helper.Increment;        return Tuple.Create(show, increment);    }    class ActionHelper    {        public int counter;        public void Show()        { Console.WriteLine(counter);        }        public void Increment()        { counter++;        }    }}