using System.Collections;
using System.Collections.Generic;

//添加一个keyvalue键值对：
HashtableObject.Add(key,value);

//移除某个keyvalue键值对：
HashtableObject.Remove(key);

//移除所有元素：           
HashtableObject.Clear(); 

// 判断是否包含特定键key：
HashtableObject.Contains(key);

using System;
using System.Collections; //file使用Hashtable时，必须引入这个命名空间
class Program
{
  public static void Main()
  {
     Hashtable ht = new Hashtable(); //创建一个Hashtable实例
     ht.Add("北京", "帝都"); //添加keyvalue键值对
     ht.Add("上海", "魔都");
     ht.Add("广州", "省会");
     ht.Add("深圳", "特区");

     string capital = (string)ht["北京"];
     Console.WriteLine(ht.Contains("上海")); //判断哈希表是否包含特定键,其返回值为true或false
     ht.Remove("深圳"); //移除一个keyvalue键值对
     ht.Clear(); //移除所有元素
  }
}

using System;
using System.Collections;

class Program
{
    static Hashtable GetHashtable()
    {
    　　Hashtable hashtable = new Hashtable();
　　　　
    　　hashtable.Add("名字", "小丽");
    　　hashtable.Add("年龄", 22);
    　　return hashtable;
    }

    static void Main()
    {
    　　Hashtable hashtable = GetHashtable();

    　　string name = (string)hashtable["名字"];
    　　Console.WriteLine(name);

    　　int age = (int)hashtable["年龄"];
    　　Console.WriteLine(age);
    }
}

using System;
using System.Collections;
using System.IO;

class Program
{
    static void Main()
    {
    Hashtable hashtable = new Hashtable();
    hashtable.Add(100, "西安");

    // 能转换成功
    string value = hashtable[100] as string;
    if (value != null)
    {
        Console.WriteLine(value);
    }

    // 转换失败，获取的值为null，但不会抛出错误。
    StreamReader reader = hashtable[100] as StreamReader;

    if (reader == null)
    {
         Console.WriteLine("西安不是StreamReader型");
    }

    // 也可以直接获取object值，再做判断
    object value2 = hashtable[100];
    if (value2 is string)
    {
        Console.Write("这个是字符串型: ");
        Console.WriteLine(value2);
    }
    }
}

for(DictionaryEntry de in ht) //ht为一个Hashtable实例
{
   Console.WriteLine(de.Key);  //de.Key对应于keyvalue键值对key
   Console.WriteLine(de.Value);  //de.Key对应于keyvalue键值对value
}

//遍历键
foreach (int key in hashtable.Keys)
{
    Console.WriteLine(key);
}


//遍历值
foreach (string value in hashtable.Values)
{
    Console.WriteLine(value);
}

ArrayList akeys=new ArrayList(ht.Keys); 
akeys.Sort(); //按字母顺序进行排序
foreach(string key in akeys)
{
   Console.WriteLine(key + ": " + ht[key]);  //排序后输出
}

Stopwatch sw = new Stopwatch();
Hashtable hashtable = new Hashtable();
Dictionary<string, int> dictionary = new Dictionary<string, int>();
int countNum = 1000000;

sw.Start();
for (int i = 0; i < countNum; i++)
{
    hashtable.Add(i.ToString(), i);
}
sw.Stop();
Console.WriteLine(sw.ElapsedMilliseconds);  //输出: 744

sw.Restart();
for (int i = 0; i < countNum; i++)
{
    dictionary.Add(i.ToString(), i);
}
sw.Stop();
Console.WriteLine(sw.ElapsedMilliseconds);  //输出: 489

sw.Restart();
for (int i = 0; i < countNum; i++)
{
    hashtable.ContainsKey(i.ToString());
}
sw.Stop();
Console.WriteLine(sw.ElapsedMilliseconds);  //输出: 245

sw.Restart();
for (int i = 0; i < countNum; i++)
{
    dictionary.ContainsKey(i.ToString());
}
sw.Stop();
Console.WriteLine(sw.ElapsedMilliseconds);  //输出: 192