C# 索引器

using System;  
using System.Collections.Generic;  
using System.Text;  
namespace Index  
{  
    class sample<T>  //这个类告诉我们如何使用客户端代码索引器  
    {  
        private T[] arr = new T[100];  
        public T this[int i] //索引器的签名由其形参的数量和类型组成。  
        {  
            get { return arr[i];}  
            set { arr[i] = value;}  
        }  
    }      
    class IndexerClass  
    {  
        private int[] arr = new int[100]; //定义数组  
        public int this[int index]   //索引器声明  
        {  
            get  
            {  
                if (index < 0 || index >100)  return 0;  
                return arr[index];  
            }  
            set  
            {  
                if (!(index < 0 || index > 100))  arr[index] = value;   
            }  
        }  
    }  
    class String_index  
    {  
        string[] days = { "Sun", "Mon", "Tues", "Wed", "Thurs", "Fri", "Sat" };  
        private int GetDay(string testday)  
        {  
            int i = 0;  
            foreach(string day in days)  
            {  
                if (day == testday)  return i;  
                i++;  
            }  
            return -1;  
        }  
        public int this[string day]  
        {  
            get{ return GetDay(day); }  
        }  
    }  
    class Program  
    {  
        static void Main(string[] args)  
        {  
            sample<string> string_value = new sample<string>();  
            string_value[0] = "Hello world";  
            System.Console.WriteLine(string_value[0]);  
  
            IndexerClass test = new IndexerClass();  
            //调用索引器初始化第2、4个数据  
            test[3] = 123;  
            test[5] = 1024;  
            for (int i = 0; i <= 10; i++ )  
            { System.Console.WriteLine("数据为#{0} = {1}", i, test[i]);}  
            String_index week = new String_index();  
            System.Console.WriteLine("这是一周的第{0}天", week["Tues"]);  
            Console.ReadKey();  
        }  
    }  
}  

 来源：http://blog.csdn.net/seawaywjd/article/details/7061155