Good way to get the key of the highest value of a Dictionary in C#

Question

I\'m trying to get the key of the maximum value in the Dictionary results.

This is what I have so far:

double max          


        

Answer 1

Maybe this isn't a good use for LINQ. I see 2 full scans of the dictionary using the LINQ solution (1 to get the max, then another to find the kvp to return the string.

You could do it in 1 pass with an "old fashioned" foreach:

KeyValuePair<string, double> max = new KeyValuePair<string, double>(); 
foreach (var kvp in results)
{
  if (kvp.Value > max.Value)
    max = kvp;
}
return max.Key;

Answer 2

You can sort dictionary by using OrderBy (for find min value) or OrderByDescending (for max value) then get first element. It also help when you need find second max/min element

Get dictionary key by max value:

double min = results.OrderByDescending(x => x.Value).First().Key;

Get dictionary key by min value:

double min = results.OrderBy(x => x.Value).First().Key;

Get dictionary key by second max value:

double min = results.OrderByDescending(x => x.Value).Skip(1).First().Key;

Get dictionary key by second min value:

double min = results.OrderBy(x => x.Value).Skip(1).First().Key;

Answer 3

I think using the standard LINQ Libraries this is as fast as you can go.

Answer 4

Little extension method:

public static KeyValuePair<K, V> GetMaxValuePair<K,V>(this Dictionary<K, V> source)
    where V : IComparable
{
    KeyValuePair<K, V> maxPair = source.First();
    foreach (KeyValuePair<K, V> pair in source)
    {
        if (pair.Value.CompareTo(maxPair.Value) > 0)
            maxPair = pair;
    }
    return maxPair;
}

Then:

int keyOfMax = myDictionary.GetMaxValuePair().Key;