.ForEach() 是 C# 语言的哪一部分？
如果我向某人解释以下 ForEach 功能，那么说 #2 是“LINQ foreach 方法”是否准确，或者它只是一个“List 扩展方法”未与 LINQ 正式关联？
var youngCustomers = from c in customers
where c.Age < 30
select c;
//1. traditional foreach approach
foreach (var c in youngCustomers)
{
Console.WriteLine(c.Display());
}
//2. LINQ foreach approach?
youngCustomers.ToList().ForEach(c => Console.WriteLine(c.Display()));
If I'm explaining the following ForEach feature to someone, is it accurate to say that #2 is the "LINQ foreach approach" or is it simply a "List<T> extension method" that is not officially associated with LINQ?
var youngCustomers = from c in customers
where c.Age < 30
select c;
//1. traditional foreach approach
foreach (var c in youngCustomers)
{
Console.WriteLine(c.Display());
}
//2. LINQ foreach approach?
youngCustomers.ToList().ForEach(c => Console.WriteLine(c.Display()));
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它是
List的普通方法，尽管人们经常为其他IEnumerable提供自己的扩展方法。 LINQ 不提供 ForEach 扩展，因为它的设计目标是由于功能性/使用不可变类型，ForEach 本质上是一种副作用/命令性操作。it is a normal method of
List<T>though people often provide their own extension methods for otherIEnumerable<T>. LINQ does not provide a ForEach extension due to its design goals of being functional/ working with immutable types, ForEach is an inherently side effect/imperative operation.它与 LINQ 无关，也不是扩展方法。
ForEach是一个简单的实例方法List类。（如果您真的很挑剔，那么
ForEach根本不是 C# 语言的一部分：它是 .NET 基类库的一部分。）It has nothing to do with LINQ and it's not an extension method.
ForEachis a plain instance method on theList<T>class.(And if you wanted to be really nitpicky, then
ForEachis not part of the C# language at all: it's part of the .NET Base Class Library.)它不是
List的扩展方法，而是List的常规方法。所以它与LINQ无关。如果有的话，“正式与 LINQ 关联”和“未正式与 LINQ 关联”之间的区别实际上并不是非常有用。 LINQ 只是一堆链式扩展方法（通常在上的其他扩展方法几乎没有任何区别。最好的区别是它们驻留在 System.Linq 或 System.Something.Linq 命名空间之一。
IEnumerable上）。它与 IEnumerableIt is not an extension method of
List<T>, it is a regular method ofList<T>.So it has nothing to do with LINQ. If it had, the distinction between "officially associated with LINQ" and not officially associated with LINQ is not practically a very useful one. LINQ is simply a bunch of chained extension methods (often on
IEnumerable<T>). There is rarely any point in distinguishing it from other extension methods onIEnumerable<T>. The best distinction would be that they reside in one of theSystem.LinqorSystem.Something.Linqnamespaces.这不是 LINQ。 LINQ 的设计方面之一是标准 LINQ 方法没有副作用。 ForEach 方法会违反这一点。
Eric Lippert 有一篇关于此的博客文章：
链接
It's not LINQ. One of the design aspects of LINQ is that the standard LINQ methods do not have side-effects. The ForEach method would violate this.
Eric Lippert has a blog article all about this:
Link
让我们分解一下：
ToList是对 .net Framework 3.5 中引入的System.Linq.Enumerable.ToList()的调用ForEach是一个调用.net Framework 2.0 中引入的System.Collections.Generic.List.ForEach c =>是 c# 3.0 中引入的 lambda 表达式语法。如果您查看
List.ForEach ，您可以看到当时调用它所需的旧委托语法。Let's break it down:
ToListis a call toSystem.Linq.Enumerable.ToList()introduced in .net framework 3.5ForEachis a call toSystem.Collections.Generic.List<T>.ForEachintroduced in .net framework 2.0c =>is lambda expression syntax introduced in c# 3.0.If you look at the documentation for
List<T>.ForEach, you can see the old delegate syntax that was required back then to call it.副作用 foreach 将在 Visual Studio 2010 的 Linq 扩展中提供 ( is )。
Side-effecting foreach will be ( is ) provided in Visual Studio 2010's Linq extensions.