摘要:System.Collection的簡介
在.Net Framework 4.5中，System.Collections Namespaces包含下列五個：[1]
第一、The System.Collections namespace contains interfaces and classes that define various collections of objects, such as lists, queues, bit arrays, hash tables and dictionaries.(自.Net Framework 1.1版開始支援[2])
第二、The System.Collections.Concurrent namespace provides several thread-safe collection classes that should be used in place of the corresponding types in the System.Collections and System.Collections.Generic namespaces whenever multiple threads are accessing the collection concurrently.(自.Net Framework 4.0版開始支援[3])
第三、The System.Collections.Generic namespace contains interfaces and classes that define generic collections, which allow users to create strongly typed collections that provide better type safety and performance than non-generic strongly typed collections.(自.Net Framework 2.0版開始支援[4])
第四、The System.Collections.ObjectModel namespace contains classes that can be used as collections in the object model of a reusable library. Use these classes when properties or methods return collections.(自.Net Framework 2.0版開始支援[5])
第五、The System.Collections.Specialized namespace contains specialized and strongly-typed collections; for example, a linked list dictionary, a bit vector, and collections that contain only strings.(自.Net Framework 1.1版開始支援[6])
參考資料來源：
[1]System.Collections Namespaces
http://msdn.microsoft.com/en-us/library/gg145035(v=vs.110).aspx
[2]System.Collections Namespace
http://msdn.microsoft.com/en-us/library/system.collections(v=vs.71).aspx
[3]System.Collections.Concurrent Namespace
http://msdn.microsoft.com/en-us/library/system.collections.concurrent(v=vs.100).aspx
[4]System.Collections.Generic Namespace
http://msdn.microsoft.com/en-us/library/system.collections.generic(v=vs.80).aspx
[5]System.Collections.ObjectModel Namespace
http://msdn.microsoft.com/en-us/library/system.collections.objectmodel(v=vs.80).aspx
[6]System.Collections.Specialized Namespace
http://msdn.microsoft.com/en-us/library/system.collections.specialized(v=vs.71).aspx
延伸資料來源：
[1].NET Framework Versions and Dependencies (.Net Framework 4)
http://msdn.microsoft.com/en-us/library/vstudio/bb822049(v=vs.100).aspx
[2].NET Framework Versions and Dependencies (.Net Framework 4.5)
http://msdn.microsoft.com/en-us/library/vstudio/bb822049(v=vs.110).aspx