Count things with a dictonary without permanently check for existance?

Question

Today I use code like this to count things:

Dictionary<string,int> wordCount = new Dictionary<string,int>();
if (!wordCount.ContainsKey(word))
{
    wordCount.Add(word, 0);
}
wordCount[word]++;

Is there a more elegant way to count things without permanently check existence?

I would like to do something like:

Dictionary<string,int> wordCount = new Dictionary<string,int>();
wordCount[word]++;

And values for the new key should automatically be initialized with a default value (0 for int for example).

Is there an elegant way to have this?

Thanks in advance.

Answer 1

You could define an extension method for dictionaries like this:

public static class DictionaryExtension
{
    public static void AddCount<T>(this Dictionary<T, int> dict, T key)
    {
        if (dict.ContainsKey(key))
        {
            dict[key]++;
        }
        else
        {
            dict[key] = 1;
        }
    }
}

You can then use it like this:

Dictionary<string, int> count = new Dictionary<string, int>();
count.AddCount("foo");
count.AddCount("bar");
count.AddCount("foo");

To go further, you could derive a new type from Dictionary and introduce a new indexer:

public class FancyDict<T> : Dictionary<T,int>
{
    public new int this[T key]
    {
        get => this.ContainsKey(key) ? base[key] : 0;
        set => base[key] = value;
    }
}

This makes it possible to use the [] syntax:

FancyDict<string> fancyCount = new FancyDict<string>();
fancyCount["foo"]++;
fancyCount["bar"]++;
fancyCount["foo"]++;

foreach (var key in fancyCount.Keys)
{
    Console.WriteLine(key + " : " + fancyCount[key]);
}