using System;using System.Collections; namespace HashtableExample{  class Program  {    static Hashtable hashtable = new Hashtable();    static void Main(string[] args)    {      hashtable.Add("first", "Beijing");      hashtable.Add("second", "Shanghai");      hashtable.Add("third", "Hangzhou");      hashtable.Add("forth", "Nanjing");       //遍歷方法一：遍歷哈希表中的鍵      foreach (string key in hashtable.Keys)      {        Console.WriteLine(hashtable[key]);      }      Console.WriteLine("--------------------");       //遍歷方法二：遍歷哈希表中的值      foreach(string value in hashtable.Values)      {        Console.WriteLine(value);      }      Console.WriteLine("--------------------");       //遍歷方法三：遍歷哈希表中的鍵值      foreach (DictionaryEntry de in hashtable)      {        Console.WriteLine(de.Value);      }      Console.WriteLine("--------------------");       //遍歷方法四：遍歷哈希表中的鍵值      IDictionaryEnumerator myEnumerator = hashtable.GetEnumerator();      while (myEnumerator.MoveNext())      {        Console.WriteLine(hashtable[myEnumerator.Key]);      }    }  }}