As a result, it is possible to optimize the implementation of a number of methods that benefit from a knowledge of the entire set of keys.

Read-only implementations must implement GetInternalKeysCollection()()()() and Get(Object). Read/write implementations must additionally implement Insert(Object, Object, Int64) and Remove(Object). If the implementation has any cost of returning an "old value", then the InsertAll(IDictionary) and RemoveBlind(Object) methods should also be implemented. The only other obvious method for optimization is Clear()()()(), if the implementation is able to do it in bulk.