IEnumerable中的更新项目 [英] Update item in IEnumerable

问题描述

我需要更新IEnumerable列表中的值.

I need to update a value in a IEnumerable list.

这是一个简短的IEnumerable示例:

Here is a brief IEnumerable example:

IEnumerable<string> allsubdirs = new List<string>() { "a", "b", "c" };

现在，如果我想为每个项目添加时间戳，则此方法将无效:

Now if I want to add a timestamp to each item, this doesnt work:

allsubdirs.Select(a => a = a + "_" + DateTime.Now.ToString("hhmmss")).ToList();

这也不是:

foreach (var item in allsubdirs)
            item = item + "_" + DateTime.Now.ToString("hhmmss");

我使它像这样工作:

IEnumerable<string> newallsubdirs = allsubdirs.Select(a => a + "_" + DateTime.Now.ToString("hhmmss")).ToList();
        allsubdirs = newallsubdirs;

但是这似乎有点像作弊.请问这样做的正确方法是什么?

but this somehow seems like cheating. Whats the proper way of doing this please?

推荐答案

Linq用于查询，而不是更新. Linq查询根据投影，过滤器等返回 new 集合.因此，您可以选择:

Linq is for querying, not updating. Linq queries return a new collection based on projections, filters etc. So your choices are:

• 将新"集合保存回变量(或在必要时添加新变量):

• Save the "new" collection back to the variable (or a new variable, if necessary):

allsubdirs = allsubdirs.Select(a => a = a + "_" + DateTime.Now.ToString("hhmmss")).ToList();

使用可写接口，例如IList<T>和for循环:

Use a writable interface like IList<T> and a for loop:

IList<string> allsubdirs = new List<string>() { "a", "b", "c" };

for(int i=0; i<allsubdirs.Count(); i++)
    allsubdirs[i] = allsubdirs[i] + "_" + DateTime.Now.ToString("hhmmss");

主要区别在于，Select 不会修改原始集合，而for循环会进行修改.

The main difference is that Select does not modify the original collection, while the for loop does.

我的观点是Select更加整洁，而不是作弊"-您只是在原始集合的顶部添加投影.

My opinion is that the Select is cleaner and is not "cheating" - you're just adding a projection on top of the original collection.

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