在列表与下更改元素的值; T> .ForEach的ForEach方法 [英] Changing element value in List<T>.ForEach ForEach method

问题描述

我有以下代码：

newsplit.ToList().ForEach(x => x = "WW");

我期望列表中的所有元素现在是WW，但他们仍然是原来的值。怎么来的？我有什么做的有什么不同？

I would expect that all elements in the list are now "WW" but they are still the original value. How come? What do I have to do different?

推荐答案

假设 newsplit 是一个的IEnumerable<串> ，你想要的：

Assuming that newsplit is an IEnumerable<string>, you want:

newsplit = newsplit.Select(x => "WW");

这是您当前拥有的代码等同于以下内容：

The code that you currently have is equivalent to the following:

foreach(string x in newsplit.ToList()) {
    AssignmentAction(x);
}

...

public static void AssignmentAction(string x) {
    x = "WW";
}

这方法不会修改 X 因为C＃和字符串的不变性的传递值语义的。

This method won't modify x because of the pass-by-value semantics of C# and the immutability of strings.

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