When to Use Generic Collections in C#

The following generic types correspond to existing collection types:

• List is the generic class corresponding to ArrayList.
• Dictionary is the generic class corresponding to Hashtable.
• Collection is the generic class corresponding to CollectionBase. Collection can be used as a base class, but unlike CollectionBase it is not abstract, making it much easier to use.
• ReadOnlyCollection is the generic class corresponding to ReadOnlyCollectionBase.ReadOnlyCollection is not abstract, and has a constructor that makes it easy to expose an existing List as a read-only collection.
• The Queue, Stack, and SortedList generic classes correspond to the respective nongeneric classes with the same names.
• There are several generic collection types that do not have nongeneric counterparts:
• • LinkedList is a general-purpose linked list that provides O(1) insertion and removal operations.
  • SortedDictionary is a sorted dictionary with O(log n) insertion and retrieval operations, making it a useful alternative to SortedList.
  • KeyedCollection is a hybrid between a list and a dictionary, which provides a way to store objects that contain their own keys.