Hashtable 的烦恼！

private void Button3_Click(object sender, System.EventArgs e)
  {
  
   NoSortHashTable hashtbl = new NoSortHashTable();
   hashtbl.Add("1","aaa");
   hashtbl.Add("2","aaa");
   hashtbl.Add("3","aaa");
   hashtbl.Add("4","aaa");
   foreach(string str in hashtbl.Keys)
   {
    Response.Write("key:"+str+"value:"+hashtbl[str]+"<br>");
   }
   
  }

  
 }

 public class NoSortHashTable : Hashtable
 {
  private ArrayList keys = new ArrayList();

  public NoSortHashTable()
  {
  }

  public override void Add(object key , object value)
  {
   base.Add(key,value);
   keys.Add(key);
  }

  public override ICollection Keys
  {
   get
   {
     return keys;
   }
  }

  public override void Clear()
  {
   base.Clear();
   keys.Clear();
  }

  public override void Remove(object key)
  {
   base.Remove(key);
   keys.Remove(key);

  }

  public override IDictionaryEnumerator GetEnumerator()
  {
   return base.GetEnumerator();
  }