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ForEach扩展方法(ForEach extension method)

我对一行代码感到困惑:

Enumerable.Range(1,10).ToList().ForEach(Console.WriteLine);

这条线做了它所说的,它打印出每个数字从1到10,每个数字之间有一个换行符,所有这些只有一条简洁的代码行。

现在我只是一个C#新手,但它对我来说看起来完全陌生,我们如何调用Console.WriteLine()而不提供任何参数? 它是如何知道打印的? 从这个语法来看,我甚至都不清楚我们正在调用一个方法(考虑到WriteLine周围缺乏语法)。

我假设这里有很多东西在“幕后”,但是我不太擅长阅读IL代码,从我收集的读取MSIL看起来似乎ForEach称为泛型委托( System.Action )对集合中的每个元素,我猜它然后将元素作为参数传递给System.Action委托,但这只是我的猜测..


I'm a bit confused over a line of code:

Enumerable.Range(1,10).ToList().ForEach(Console.WriteLine);

This line does what it says it does, it prints out each number from 1 to 10 with a line break inbetween each of them, all that with one neat little line of code..

Now I'm only a C# novice at best, but it looks completely foreign to me, how can we call Console.WriteLine() without providing it with any arguments? How does it know what it's going to print? From this syntax it's not even clear to me that we're calling on a method (considering the lack of paranthesis around WriteLine).

I'm assuming that there's a lot of stuff going on "behind the scenes" here but I'm not very good at reading IL code, from what I've gathered reading the MSIL it seems like ForEach calls a generic delegate(System.Action) on each element in the collection, I am guessing that it then passes the element as an argument to the System.Action delegate but that's only my guess..


原文:https://stackoverflow.com/questions/23175077
更新时间:2020-03-26 12:00

最满意答案

从方法组(在本例中为Console.WriteLine )和兼容的委托类型进行隐式转换。 你的代码实际上和

Action<int> f = Console.WriteLine;
Enumerable.Range(1,10).ToList().ForEach(f);

委托f与方法void Console.WriteLine(int)兼容


There is an implicit conversion from a method group (Console.WriteLine in this case) and a compatible delegate type. You code is effectively the same as

Action<int> f = Console.WriteLine;
Enumerable.Range(1,10).ToList().ForEach(f);

The delegate f is compatible with the method void Console.WriteLine(int)

2014-04-19

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