我的linq select不起作用，我的foreach起作用 [英] My linq select does not work, my foreach does

问题描述

我有以下不起作用的LINQ Select.

I have the following LINQ Select which does not work.

Data.Select(d => d.Value.IsDirty = true); //-- Not working

我的解决方法更长.

foreach (var d in Data)
    d.Value.IsDirty = true;

为什么我的第一个代码不起作用?

Why does my first code not work?

推荐答案

Select()返回一个IEnumerable<…>，该IEnumerable<…>具有功能可以遍历输入并调用有问题的代码，但是除非您以某种方式枚举，否则实际上不会这样做:

Select() returns an IEnumerable<…>, which has the ability to iterate over the input and invoke the code in question, but doesn't actually do so until you enumerate it in some manner:

Data.Select(d => d.Value.IsDirty = true).ToList();

或

foreach (var _ in Data.Select(d => d.Value.IsDirty = true))
    ; // Do nothing

但是，考虑到它们会产生副作用(显然是在这里的意图)，以上两种都是不好的业力.不要使用它们.原始的foreach是唯一明智的选择.

However, given that they perform side effects (obviously the intent here), both of the above are bad karma. Don't use them. Your original foreach is the only sensible choice.

这篇关于我的linq select不起作用，我的foreach起作用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！