为什么 Enumerable.All 为空序列返回 true? [英] Why does Enumerable.All return true for an empty sequence?

问题描述

var strs = new Collection<string>();
bool b = strs.All(str => str == "ABC");

代码创建一个空的字符串集合，然后尝试确定集合中的所有元素是否都是ABC".如果你运行它，b 将为真.

The code creates an empty collection of string, then tries to determine if all the elements in the collection are "ABC". If you run it, b will be true.

但该集合中甚至没有任何元素，更不用说任何等于ABC"的元素了.

But the collection does not even have any elements in it, let alone any elements that equal to "ABC".

这是一个错误，还是有合理的解释?

Is this a bug, or is there a reasonable explanation?

推荐答案

这当然不是错误.它的行为完全如文档所述:

It's certainly not a bug. It's behaving exactly as documented:

如果源序列的每个元素都通过了指定谓词中的测试，则为真，或者如果序列为空；否则为假.

true if every element of the source sequence passes the test in the specified predicate, or if the sequence is empty; otherwise, false.

现在你可以争论它是否应该那样工作(对我来说似乎很好；序列的每个元素都符合谓词)但是首先要检查 在你问是否有问题之前，先看看文档.(当方法的行为与您预期的不同时，首先要检查它.)

Now you can argue about whether or not it should work that way (it seems fine to me; every element of the sequence conforms to the predicate) but the very first thing to check before you ask whether something is a bug, is the documentation. (It's the first thing to check as soon as a method behaves in a way other than what you expected.)

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