含參屬性:接收一個或者多個參數屬性.


類似數組的語法來訪問。this[]

1.查看.NET文檔時以查找我為Item的屬性來判斷是否支持索引器
using System;
using System.Collections;
namespace TestIndex
{
	/// <summary>
	/// Class1 的摘要說明。
	/// </summary>
	class Class1
	{
		/// <summary>
		/// 應用程序的主入口點。
		/// </summary>
		[STAThread]
		static void Main(string[] args)
		{
			SortedList mysort=new SortedList();
			mysort.Add("ge",30);
			mysort.Add("hu",28);
			mysort.Add("chi",25);
			
			//支持索引器,文檔中SortedList有Item屬性
			Console.WriteLine(mysort["hu"].ToString());
			//迭代輸出(通常)
			for ( int i = 0; i < mysort.Count; i++ )  
			{
				Console.WriteLine( "\t{0}:\t{1}", mysort.GetKey(i), mysort.GetByIndex(i) );
			}

		}
	}
}




2.索引器實現的一個例子

using System;
namespace Movecont
{
		public class BitArray
		{
			private Byte[]byteArray;
			private Int32 numBits;
			public BitArray(Int32 numBits)
			{
				if(numBits<=0)
					throw new ArgumentOutOfRangeException("numBits","numBits must be>0");
				this.numBits=numBits;
				byteArray=new Byte[(numBits+7)/8];
			}
			public Boolean this[Int32 bitPos]
			{
				get
				{
					if((bitPos<0)||(bitPos>=numBits))
						throw new IndexOutOfRangeException();
					return (byteArray[bitPos/8]&(1<<(bitPos%8)))!=0;
				}
				set
				{
					if((bitPos<0)||(bitPos>=numBits))
						throw new IndexOutOfRangeException();
					if(value)
					{
						byteArray[bitPos/8]=(Byte)(byteArray[bitPos/8]|(1<<(bitPos%8)));
					}
					else
					{
						byteArray[bitPos/8]=(Byte)(byteArray[bitPos/8]&~(1<<(bitPos%8)));
					}
					
			}
		}
	}
	class App
	{
		static void Main()
		{
			BitArray ba=new BitArray(14);
			for(Int32 x=0;x<14;x++)
				ba[x]=(x%2==0);
			for(Int32 x=0;x<14;x++)
				Console.WriteLine("Bit "+x+" is "+(ba[x]?"On":"Off"));	
		}	
	}
}

3.改變編譯器產生的名稱,讓其它語言訪問

	[System.Runtime.CompilerServices.IndexerName("Bit")]
			public Boolean this[Int32 bitPos]
			{


VB

Dima ba As New BitArray(10)

Console.WriteLine(ba(2));

Console.WriteLine(ba.Bit(2)); //通過名稱訪問

4.System.String類型就是一個改變索引器名稱的例子Chars,而非Item


			string s="gelifeng";
			Console.WriteLine(s[1].ToString());