NameValueCollection詳解

1.NameValueCollection類集合是基於 NameObjectCollectionBase 類。

但與 NameObjectCollectionBase 不同，該類在一個鍵下存儲多個字符串值（就是鍵相同，值就連接起來如下例子）。該類可用於標頭、查詢字符串和窗體數據。
每個元素都是一個鍵/值對。NameValueCollection 的容量是 NameValueCollection 可以保存的元素數。
NameValueCollection 的默認初始容量爲零。隨着向 NameValueCollection 中添加元素，容量通過重新分配按需自動增加。
如下例子：

NameValueCollection myCol = new NameValueCollection();
            myCol.Add("red", "rojo");//如果鍵值red相同結果合併 rojo,rouge
            myCol.Add("green", "verde");
            myCol.Add("blue", "azul");
            myCol.Add("red", "rouge");

2.NameValueCollection與Hashtable的區別

a.引用區別

hashtable:using System.Collections;

NameValueCollection:using System.Collections.Specialized; 

b.鍵是否重複

NameValueCollection:允許重複.

HashTable是鍵-值集合,但鍵不能出現重複. 

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

3.初始化NameValueCollection 

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

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");//如果鍵值red相同結果合併 rojo,rouge
            myCol.Add("green", "verde");
            myCol.Add("blue", "azul");
            myCol.Add("red", "rouge");

            // Displays the values in the NameValueCollection in two different ways.
            //顯示鍵，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.
            //按索引或值獲取
            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"]);//鍵爲red的對應值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鍵值然後刪除
            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);

        }
        //顯示鍵，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();
        }
        //顯示索引, 鍵,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遍歷 

與Hashtable相似: 

NameValueCollection myCol = new NameValueCollection();
myCol.Add("red", "rojo");//如果鍵值red相同結果合併 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();

轉自:http://blog.csdn.net/a497785609/article/details/5702356