What is the difference between Sorted Dictionary and Ordered Dictionary?

There are 3 main difference. 1. The namespaces OrderedDictionary => System.Collections.Specialized; SortedDictionary => System.Collections.Generic; 2. In SortedDictionary key/pair is sorted by key but not in OrderedDictionary. 3. In OrderedDictionary values can access either with key or index. In SortedDictionary values are only access through key.