NameValueCollection详解

1.NameValueCollection类集合是基于 NameObjectCollectionBase 类。
但与 NameObjectCollectionBase 不同，该类在一个键下存储多个字符串值（就是键相同，值就连接起来如下例子）。该类可用于标头、查询字符串和窗体数据。
每个元素都是一个键/值对。NameValueCollection 的容量是 NameValueCollection 可以保存的元素数。
NameValueCollection 的默认初始容量为零。随着向 NameValueCollection 中添加元素，容量通过重新分配按需自动增加。
如下例子：

NameValueCollection myCol = new NameValueCollection(); 
            myCol.Add("red", "rojo");//如果键值red相同结果合并 rojo,rouge 
            myCol.Add("green", "verde"); 
            myCol.Add("blue", "azul"); 
            myCol.Add("red", "rouge"); 

2.NameValueCollection与Hashtable的区别
a.引用区别

hashtable:using System.Collections;

NameValueCollection:using System.Collections.Specialized;

b.键是否重复

NameValueCollection:允许重复.

HashTable是键-值集合,但键不能出现重复.

Hashtable ht = new Hashtable(); 
ht.Add("key","value"); 
ht.Add("key", "value1"); //出错 
ht["key"] = "value1"; //正确 

3.初始化NameValueCollection
初始化NameValueCollection需引用using System.Collections.Specialized;
完整例子源码：

using System;  using System.Collections; 
using System.Collections.Specialized; 
 
namespace SamplesNameValueCollection 
{ 
    class Program 
    { 
 
        public static void Main() 
        { 
            //初始化NameValueCollection需引用using System.Collections.Specialized; 
            NameValueCollection myCol = new NameValueCollection(); 
            myCol.Add("red", "rojo");//如果键值red相同结果合并 rojo,rouge 
            myCol.Add("green", "verde"); 
            myCol.Add("blue", "azul"); 
            myCol.Add("red", "rouge"); 
 
            // Displays the values in the NameValueCollection in two different ways. 
            //显示键，值 
            Console.WriteLine("Displays the elements using the AllKeys property and the Item (indexer) property:"); 
            PrintKeysAndValues(myCol); 
            Console.WriteLine("Displays the elements using GetKey and Get:"); 
            PrintKeysAndValues2(myCol); 
 
            // Gets a value either by index or by key. 
            //按索引或值获取 
            Console.WriteLine("Index 1 contains the value {0}.", myCol[1]);//索引1的值 
            Console.WriteLine("Key \"red\" has the value {0}.", myCol["red"]);//键为red的对应值rouge 
            Console.WriteLine(); 
 
            // Copies the values to a string array and displays the string array. 
            String[] myStrArr = new String[myCol.Count]; 
            myCol.CopyTo(myStrArr, 0); 
            Console.WriteLine("The string array contains:"); 
            foreach (String s in myStrArr) 
                Console.WriteLine("   {0}", s); 
            Console.WriteLine(); 
 
            //查找green键值然后删除 
            myCol.Remove("green"); 
            Console.WriteLine("The collection contains the following elements after removing \"green\":"); 
            PrintKeysAndValues(myCol); 
 
            //清空集合 
            myCol.Clear(); 
            Console.WriteLine("The collection contains the following elements after it is cleared:"); 
            PrintKeysAndValues(myCol); 
 
        } 
        //显示键，值 
        public static void PrintKeysAndValues(NameValueCollection myCol) 
        { 
            IEnumerator myEnumerator = myCol.GetEnumerator(); 
            Console.WriteLine("   KEY        VALUE"); 
            foreach (String s in myCol.AllKeys) 
                Console.WriteLine("   {0,-10} {1}", s, myCol[s]); 
            Console.WriteLine(); 
        } 
        //显示索引, 键,值 
        public static void PrintKeysAndValues2(NameValueCollection myCol) 
        { 
            Console.WriteLine("   [INDEX] KEY        VALUE"); 
            for (int i = 0; i < myCol.Count; i++) 
                Console.WriteLine("   [{0}]     {1,-10} {2}", i, myCol.GetKey(i), myCol.Get(i)); 
            Console.WriteLine(); 
        } 
    } 
 
} 
4.NameValueCollection遍历
与Hashtable相似:

NameValueCollection myCol = new NameValueCollection();   
myCol.Add("red", "rojo");//如果键值red相同结果合并 rojo,rouge   
myCol.Add("green", "verde");   
myCol.Add("blue", "azul"); 
myCol["red"] = "dd"; 
 
foreach (string key in myCol.Keys) 
{ 
    Console.WriteLine("{0}:{1}", key, myCol[key]); 
} 
Console.ReadLine();