Standard Collection

下表列出了 System.Collections 命名空间中最重要的集合类：

Class Description
ArrayList The ArrayList is a general-purpose list that stores a linear collection of objects. The ArrayList includes methods and properties that enable you to add items, remove items, count the number of items in the collection, and sort the collection.
BitArray The BitArray is a list class that represents a collection of bits as Boolean values. The BitArray is most commonly used for bitwise operations and Boolean arithmetic, and includes methods to perform common Boolean operations such as AND, NOT, and XOR.
Hashtable The Hashtable class is a general-purpose dictionary class that stores a collection of key/value pairs. The Hashtable includes methods and properties that enable you to retrieve items by key, add items, remove items, and check for particular keys and values within the collection.
Queue The Queue class is a first in, first out collection of objects. The Queue includes methods to add objects to the back of the queue (Enqueue) and retrieve objects from the front of the queue (Dequeue).
SortedList The SortedList class stores a collection of key/value pairs that are sorted by key. In addition to the functionality provided by the Hashtable class, the SortedList enables you to retrieve items either by key or by index.
Stack The Stack class is a first in, last out or last in, first out (LIFO) collection of objects. The Stack includes methods to view the top item in the collection without removing it (Peek), add an item to the top of the stack (Push), and remove and return the item at the top of the stack (Pop).

Choosing Collections

选择集合类时考虑以下几个问题：

  • 是否需要对集合排序？

  • 集合大概多大？

  • 使用 index 序号还是用 key 去检索集合内的元素？

  • 集合是否仅由字符串组成？

Specialized Collections

System.Collections.Specialized 命名空间内包含一批用于特定用途的集合类：

Class Description
ListDictionary The ListDictionary is a dictionary class that is optimized for small collections. As a general rule, if your collection includes 10 items or fewer, use a ListDictionary. If your collection is larger, use a Hashtable.
HybridDictionary The HybridDictionary is a dictionary class that you can use when you cannot estimate the size of the collection. The HybridDictionary uses a ListDictionary implementation when the collection size is small, and switches to a Hashtable implementation as the collection size grows larger.
OrderedDictionary The OrderedDictionary is an indexed dictionary class that enables you to retrieve items by key or by index. Note that unlike the SortedList class, items in an OrderedDictionary are not sorted by key.
NameValueCollection The NameValueCollection is an indexed dictionary class in which both the key and the value are strings. The NameValueCollection will throw an error if you attempt to set a key or a value to anything other than a string. You can retrieve items by key or by index.
StringCollection The StringCollection is a list class in which every item in the collection is a string. Use this class when you want to store a simple, linear collection of strings..
StringDictionary The StringDictionary is a dictionary class in which both the key and the value are strings. Unlike the NameValueCollection class, you cannot retrieve items from a StringDictionary by index.
BitVector32 The BitVector32 is a struct that can represent a 32-bit value as both a bit array and an integer value. Unlike the BitArray class, which can expand indefinitely, the BitVector32 struct is a fixed 32-bit size. As a result, the BitVector32 is more efficient than the BitArray for small values. You can divide a BitVector32 instance into sections to efficiently store multiple values.

学习资源：