NameValueCollection詳解

1.NameValueCollection類集合是基于 NameObjectCollectionBase 類。

但與 NameObjectCollectionBase 不同，該類在一個鍵下存儲多個字元串值（就是鍵相同，值就連接配接起來如下例子）。該類可用于标頭、查詢字元串和窗體資料。

每個元素都是一個鍵/值對。NameValueCollection 的容量是 NameValueCollection 可以儲存的元素數。

NameValueCollection 的預設初始容量為零。随着向 NameValueCollection 中添加元素，容量通過重新配置設定按需自動增加。

如下例子：

NameValueCollection myCol = new NameValueCollection();  

            myCol.Add("red", "rojo");//如果鍵值red相同結果合并 rojo,rouge  

            myCol.Add("green", "verde");  

            myCol.Add("blue", "azul");  

            myCol.Add("red", "rouge");  

2.NameValueCollection與Hashtable的差別

a.引用差別

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"; //正确  

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();  

            // 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.  

            //按索引或值擷取  

            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"]);//鍵為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);  

            //查找green鍵值然後删除  

            myCol.Remove("green");  

            Console.WriteLine("The collection contains the following elements after removing \"green\":");  

            //清空集合  

            myCol.Clear();  

            Console.WriteLine("The collection contains the following elements after it is cleared:");  

        }  

        //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]);  

        //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));  

    }  

}  

4.NameValueCollection周遊

與Hashtable相似:

NameValueCollection myCol = new NameValueCollection();    

myCol.Add("red", "rojo");//如果鍵值red相同結果合并 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();  

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