Is there an IDictionary implementation that, on missing key, returns the default value instead of throwing?

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.