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I basically want to know how to write this (Extract all keys from a list of dictionaries) in C#.

I have a list of dictionaries which have all unique keys.

I want to extract all of them into a list of string (as the key is string).

private List<Dictionary<string, string>> dictList = new List<Dictionary<string, string>> { new Dictionary<string, string>() { { "a", "b" } }, new Dictionary<string, string>() { { "c", "d" } }, }; private void GetDictListKeys() { List<string> keyList = new List<string>(); foreach(var dict in dictList) { keyList.Add(dict.Keys.ToString()); } }

Thank you.

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3 Answers 3

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5

You want to flatten your enumerable of keys and dump it into a collection (HashSet used cause you mentioned duplicates, and because that's also what your linked answer used in Python):

var allKeys = dictList.SelectMany(d => d.Keys).ToHashSet();
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2 Comments

If you actually want a list, use ToList() instead.
... or if you want unique keys but a list use dictList.SelectMany(d => d.Keys).Distinct().ToList()
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You can use AddRange.

 foreach (var dict in dictList) { keyList.AddRange(dict.Keys); }
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1 Comment

Another beautiful way to get what I wanted. Thank you!
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You can create another foreach loop inside yours:

foreach (Dictionary<string,string> dict in dictList) { foreach(string key in dict.Keys) { keyList.Add(key); } }
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Couldn't really think of having two loops! Thank you very much!

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