My KeyedList<TKey, TValue> generic class sample has been update to include a method that sorts string keys in about half the List<T> class sort time.
This way you can add string keys to KeyedList and then sort instead of using the SortedList collection. In the case of string key types it will take longer to add the keys to SortedList. (And SortedList is faster than SortedDictionary.)
My new Fast List Sort in C# article also has methods to customize string sorting for a specialized List<string> collection.