Is there an IDictionary implementation that returns null on missing key instead of throwing?

Question

The indexer into Dictionary throws an exception if the key is missing. Is there an implementation of IDictionary that instead will return default(T)?

I know about the "TryGetValue" method, but that's impossible to use with linq.

Would this efficiently do what I need?:

myDict.FirstOrDefault(a => a.Key == someKeyKalue);

I don't think it will as I think it will iterate the keys instead of using a Hash lookup.

Answer 1

No, because otherwise how would you know the difference when the key exists but stored a null value? That could be significant.

Answer 2

Indeed, that won't be efficient at all.

You could always write an extension method:

public static TValue GetValueOrDefault<TKey,TValue>
    (this IDictionary<TKey, TValue> dictionary, TKey key)
{
    TValue ret;
    // Ignore return value
    dictionary.TryGetValue(key, out ret);
    return ret;
}