Collections(Chapter 7 of C# 4.0 in a nutshell)

　　Although the enumeration interfaces provide a protocol for forward-only iteration over a collection, they don’t provide a mechanism to determine the size of the collection, access a member by index, search, or modify the collection. For such functionality, the .NET Framework defines the ICollection, IList, and IDictionary interfaces. Each comes in both generic and nongeneric versions; however, the nongeneric versions exist mostly for legacy.

 

　　IEnumerable<T> (and IEnumerable)

　　Provides minimum functionality (enumeration only)

 

　　ICollection<T> (and ICollection)

　　Provides medium functionality (e.g., the Count property)

 

　　IList <T>/IDictionary <K,V> and their nongeneric versions

　　Provide maximum functionality (including “random” access by index/key)