Basically I want something like Dictionary<Tkey1, TKey2, TValue>, but not (as I've seen here in other question) with the keys in AND, but in OR. To better explain: I want to be able to find an element in the dictionary providing just one of the keys, not both.
I also think we should consider thread-safety and the ability to easily scale to a Dictionary<Tkey1, TKey2, TKeyN, TValue> solution...