C# SortedList类

using System;
using System.Collections;

namespace CollectionsApplication {

   class Program {

      static void Main(string[] args) {
         SortedList sl = new SortedList();

         sl.Add(001, Zara Ali);
         sl.Add(002, Abida Rehman);
         sl.Add(003, Joe Holzner);
         sl.Add(004, Mausam Benazir Nur);
         sl.Add(005, M. Amlan);
         sl.Add(006, M. Arif);
         sl.Add(007, Ritesh Saikia);

         if (sl.ContainsValue(Nuha Ali)) {
            Console.WriteLine(This student name is already in the list);
         } else {
            sl.Add(008, Nuha Ali);
         }

         // get a collection of the keys. 
         ICollection key = sl.Keys;

         foreach (string k in key) {
            Console.WriteLine(k + :  + sl[k]);
         }
      }
   }
}