Get all keys in Dictionary containing value x

Question

I have this:

Dictionary dict = new Dictionary();

I want to select all the items in the dictionary

Answer 1

Well it's reasonably simple with LINQ:

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

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

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.