为什么不能为每个循环修改一个集合 [英] Why can't you modify a collection in a for each loop

问题描述

如果你复制它，为什么能最好地解释为什么要替换使用foreach循环的集合元素？示例：

How can you best explain why replacing an element of a collection you are looping using foreach is permited if you make a copy of it. Example:

foreach(Item item in Items)
{
   item.modify //or remove or add
}
// will not work

foreach(Item item in Items.ToList())
{
   item.modify //or remove. or add
}

//will work altough i dont get it because i am now iterating trough the temporary list
//and changing its elements. 
//In my understanding its not like im iterating the list(.ToList) and modifying the source items
//(Items). A graphic representation would be welcome, my interest is to understand the
//matter logically

推荐答案

最佳答案是List对其列表项进行某种跟踪，并且可以按照您的要求更新其项目，但是简单的IEnumerable不会这样，因此它不允许您更改它们。

The Best answer would be that List has some kind of Tracking over its list items and can update its items as you ask but a simple IEnumerable does not so it will not allow you to change them.

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