获取字典中包含值x的所有键 [英] Get all keys in Dictionary containing value x

问题描述

我有这个:

Dictionary<integer, string> dict = new Dictionary<integer, string>();

我想选择字典中包含值abc的所有项目.

I want to select all the items in the dictionary that contain the value abc.

有内置的函数可以让我轻松地做到这一点吗?

Is there an inbuilt function that lets me do this easily?

推荐答案

使用LINQ，合理很简单:

Well it's reasonably simple with LINQ:

var matches = dict.Where(pair => pair.Value == "abc")
                  .Select(pair => pair.Key);

请注意，这甚至效率不高-这是O(N)操作，因为它需要检查每个条目.

Note that this won't be even slightly efficient - it's an O(N) operation, as it needs to check every entry.

如果您需要经常执行此操作，则可能要考虑使用其他数据结构-Dictionary<,>是专门为通过键快速查找而设计的.

If you need to do this frequently, you may want to consider using another data structure - Dictionary<,> is specifically designed for fast lookups by key.

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