Which name for a "smart" dictionary (hashtable)?

I'm looking for a good name for a custom dictionary which automatically initializes the value for a requested key if it doesn't exist, using a delegate. The indexer implementation should help understand what it does :

    public V this[K ke开发者_StackOverflowy]
    {
        get
        {
            V value;
            if (!_dictionary.TryGetValue(key, out value))
            {
                value = _defaultValueGenerator(key);
                _dictionary[key] = value;
            }
            return value;
        }
        set
        {
            _dictionary[key] = value;
        }
    }

My problem is not about the code, which works fine, but I can't seem to find a proper name for this class... I thought about AutoInitDictionary, but it doesn't sound right, and doesn't really conveys the idea that "all keys can be assumed to exist".

How would you name such a class ? Any suggestion would be appreciated.

PS: an example of how it could be used :

var charFrequencies = new AutoInitDictionary<char, int>(key => 0);
foreach(char c in text)
    charFrequencies[c]++;

Python has exactly this kind of dictionary, and they call it a defaultdict.

I would suggest FactoryDictionary option.

What about VirtualDictionary?

vir·tu·al (vûr'chōō-əl):

Existing or resulting in essence or effect though not in actual fact, form

Existing in the mind, especially as a product of the imagination

Being such in power, force, or effect, though not actually or expressly such

Temporarily simulated or extended by computer software

All 4 definitions somewhat relate to your implementation.

EDIT: Even DynamicDictionary will be good.

How about SmartDictionary? I thought your subject was good enough. ;)

FullDictionary ?