Which mechanism is a better way to extend Dictionary to deal with missing keys and why?

Question

There is a minor annoyance I find myself with a lot - I have a Dictionary that contains values that may or may not be there.

So norm

Answer 1

Or perhaps

public static TValue TryGet(this Dictionary input, 
                                                   TKey key)
{

     return input.ContainsKey(key) ? input[key] : *some default value*;

}