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NameValueCollection
特性: 同一個key可重複Add(). 等於append!

using System;
using System.Collections;
using System.Collections.Specialized;

public class SamplesNameValueCollection  {

   public static void Main()  {

      // Creates and initializes a new NameValueCollection.
      NameValueCollection myCol = new NameValueCollection();
      myCol.Add( "red", "rojo" );
      myCol.Add( "green", "verde" );
      myCol.Add( "blue", "azul" );
      myCol.Add( "red", "rouge" );  // 同一個key可重複Add. 等於append!

      // Displays the values in the NameValueCollection in two different ways.
      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.
      Console.WriteLine( "Index 1 contains the value {0}.", myCol[1] );
      Console.WriteLine( "Key \"red\" has the value {0}.", myCol["red"] );
      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();

      // Searches for a key and deletes it.
      myCol.Remove( "green" );
      Console.WriteLine( "The collection contains the following elements after removing \"green\":" );
      PrintKeysAndValues( myCol );

      // Clears the entire collection.
      myCol.Clear();
      Console.WriteLine( "The collection contains the following elements after it is cleared:" );
      PrintKeysAndValues( myCol );

   }

   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();
   }

   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();
   }


}

/*

This code produces the following output.

Displays the elements using the AllKeys property and the Item (indexer) property:
   KEY        VALUE
   red        rojo,rouge
   green      verde
   blue       azul

Displays the elements using GetKey and Get:
   [INDEX] KEY        VALUE
   [0]     red        rojo,rouge
   [1]     green      verde
   [2]     blue       azul

Index 1 contains the value verde.
Key "red" has the value rojo,rouge.

The string array contains:
   rojo,rouge
   verde
   azul

The collection contains the following elements after removing "green":
   KEY        VALUE
   red        rojo,rouge
   blue       azul

The collection contains the following elements after it is cleared:
   KEY        VALUE


*/

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這個範例會從 Web.config 檔讀取索引鍵 customsetting1 所識別的應用程式設定。 
appSettings 項目是字串的 NameValueCollection 集合。 
使用集合項目會比使用其他組態項目要複雜一些。


System.Configuration.Configuration rootWebConfig1 = System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration(null);
if (0 < rootWebConfig1.AppSettings.Settings.Count)
{
	System.Configuration.KeyValueConfigurationElement customSetting = rootWebConfig1.AppSettings.Settings["customsetting1"];
	if (null != customSetting)
		Console.WriteLine("customsetting1 application string = \"{0}\"", customSetting.Value);
	else
		Console.WriteLine("No customsetting1 application string");
}

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表示相關 String 索引鍵和 String 值的集合，而這些可以利用索引鍵或索引來存取。

這個集合是以 NameObjectCollectionBase 類別為基礎。 不過，不同於 NameObjectCollectionBase，這個類別是在單一索引鍵下儲存多個字串值。 

這個類別可用於標頭、查詢字串和表單資料。

每個元素都是索引鍵/值組。

NameValueCollection 的容量是 NameValueCollection 可以保存的項目數。 元素加入 NameValueCollection 時，容量會依所需透過重新配置自動增加。 

雜湊程式碼提供者分配 NameValueCollection 中索引鍵的雜湊程式碼。 預設雜湊程式碼提供者為 CaseInsensitiveHashCodeProvider。 

比較子判斷兩個索引鍵是否相等。預設比較子為 CaseInsensitiveComparer。