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How to sort Dictionary based on keys where key contains Month Year expression of DateTime as String

April 25, 2023

I am trying to sort below Dictionary

Dictionary<string, int> map = new Dictionary<string, int>();
map["Sep 20"] = 10;
map["Oct 20"] = 11;
map["Nov 20"] = 23;
map["Jan 21"] = 15;
map["Feb 20"] = 50;
map["Mar 20"] = 23;

I have tried to used SortedDictionary to sort Dictionary as follows

SortedDictionary<string, int> sortMap = new SortedDictionary<string, int>(map);

foreach (var entry in sortMap)
{
  Console.WriteLine (entry.Key+"\t"+entry.Value);
}

This is I am expecting as output

Feb 20  50
Mar 20  23
Sep 20  10
Oct 20  11
Nov 20  23
Jan 21  15

But, I am getting actual output as follows

Feb 20  50
Jan 21  15
Mar 20  23
Nov 20  23
Oct 20  11
Sep 20  10

>Solution :

You can use DateTime.ParseExact and LINQ:

 map = map
    .Select(kv => (KV: kv, DT: DateTime.ParseExact(kv.Key, "MMM yy", CultureInfo.InvariantCulture)))
    .OrderBy(x => x.DT)
    .ToDictionary(x => x.KV.Key, x => x.KV.Value);

However, if you want to use this Dictionary<TKey, TValue> you should not rely on the order if you plan to modify it. If you add or remove items, the enumerator might return the key-value-pairs in a different order. So if you have to do this often, you better use a SortedDictionary<TKey, TValue>> or a simple List<T>(T could be a class or a KeyValuePair<TKey, TValue>).