Dictionary GetOrCreate

Extensions.cs

    public static class Extensions
    {
        public static TValue GetOrCreate<TKey, TValue>(this Dictionary<TKey, TValue> d, TKey key, Func<TKey, TValue> valueFactory)
        {
            TValue value;
            if (!d.TryGetValue(key, out value))
            {
                d[key] = value = valueFactory(key);
            }
            return value;
        }
    }