c# - How do you sort a dictionary by value?

I often have to sort a dictionary, consisting of keys & values, by value. For example, I have a hash of words and respective frequencies, that I want to order by frequency.

There is a SortedList which is good for a single value (say frequency), that I want to map it back to the word.

SortedDictionary orders by key, not value. Some resort to a custom class, but is there a cleaner way?

Answer

Use:

using System.Linq.Enumerable;
...

List> myList = aDictionary.ToList();

myList.Sort(
    delegate(KeyValuePair pair1,
    KeyValuePair pair2)
    {
        return pair1.Value.CompareTo(pair2.Value);
    }
);

Since you're targeting .NET 2.0 or above, you can simplify this into lambda syntax -- it's equivalent, but shorter. If you're targeting .NET 2.0 you can only use this syntax if you're using the compiler from Visual Studio 2008 (or above).

var myList = aDictionary.ToList();

myList.Sort((pair1,pair2) => pair1.Value.CompareTo(pair2.Value));