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    using System;
    using System.Collections; //使用Hashtable时，必须引入这个命名空间
    class hashtable
    {
      public static void Main()
      {
      Hashtable ht=new Hashtable(); //创建一个Hashtable实例
      ht.Add(“E”,”e”);//添加key/value键值对
      ht.Add(“A”,”a”);
      ht.Add(“C”,”c”);
      ht.Add(“B”,”b”);
      string s=(string)ht[“A”];
      if(ht.Contains(“E”)) //判断哈希表是否包含特定键,其返回值为true或false
        Console.WriteLine(“the E key:exist”);
      ht.Remove(“C”);//移除一个key/value键值对
      Console.WriteLine(ht[“A”]);//此处输出a
      ht.Clear();//移除所有元素
      Console.WriteLine(ht[“A”]); //此处将不会有任何输出
      }
    } 

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

     ArrayList akeys=new ArrayList(ht.Keys); //别忘了导入System.Collections
     akeys.Sort(); //按字母顺序进行排序
     for(string skey in akeys)
     {
       Console.Write(skey + “:”);
       Console.WriteLine(ht[skey]);//排序后输出
     }

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

    namespace MYMD5
    {
     public class MD5
     {
     const int BITS_TO_A_BYTE = 8;
     const int BYTES_TO_A_WORD = 4;
     const int BITS_TO_A_WORD = 32;
     private static long[] m_lOnBits = new long[30 + 1];
     private static long[] m_l2Power = new long[30 + 1];

     private static long LShift(long lValue, long iShiftBits)
     {
     long LShift = 0;
     if (iShiftBits == 0)
     {
     LShift = lValue;
     return LShift;
     }
     else
     {
     if (iShiftBits == 31)
     {
     if (Convert.ToBoolean(lValue & 1))
     {
     LShift = 0x80000000;
     }
     else
     {
     LShift = 0;
     }
     return LShift;
     }
     else
     {
     if (iShiftBits 31)
     {
     // Err.Raise 6;
     }
     }
     }

     if (Convert.ToBoolean((lValue & m_l2Power[31 – iShiftBits])))
     {
     LShift = ((lValue & m_lOnBits[31 – (iShiftBits + 1)]) * m_l2Power[iShiftBits]) | 0x80000000;
     }
     else
     {
     LShift = ((lValue & m_lOnBits[31 – iShiftBits]) * m_l2Power[iShiftBits]);
     }

     return LShift;
     }

     private static long RShift(long lValue, long iShiftBits)
     {
     long RShift = 0;
     if (iShiftBits == 0)
     {
     RShift = lValue;
     return RShift;
     }
     else
     {
     if (iShiftBits == 31)
     {
     if (Convert.ToBoolean(lValue & 0x80000000))
     {
     RShift = 1;
     }
     else
     {
     RShift = 0;
     }
     return RShift;
     }
     else
     {
     if (iShiftBits 31)
     {
     // Err.Raise 6;
     }
     }
     }

     RShift = (lValue & 0x7FFFFFFE) / m_l2Power[iShiftBits];

     if (Convert.ToBoolean((lValue & 0x80000000)))
     {
     RShift = (RShift | (0x40000000 / m_l2Power[iShiftBits – 1]));
     }

     return RShift;
     }

     private static long RotateLeft(long lValue, long iShiftBits)
     {
     long RotateLeft = 0;
     RotateLeft = LShift(lValue, iShiftBits) | RShift(lValue, (32 – iShiftBits));
     return RotateLeft;
     }

     private static long AddUnsigned(long lX, long lY)
     {
     long AddUnsigned = 0;
     long lX4 = 0;
     long lY4 = 0;
     long lX8 = 0;
     long lY8 = 0;
     long lResult = 0;

     lX8 = lX & 0x80000000;
     lY8 = lY & 0x80000000;
     lX4 = lX & 0x40000000;
     lY4 = lY & 0x40000000;

     lResult = (lX & 0x3FFFFFFF) + (lY & 0x3FFFFFFF);
     if (Convert.ToBoolean(lX4 & lY4))
     {
     lResult = lResult ^ 0x80000000 ^ lX8 ^ lY8;
     }
     else if (Convert.ToBoolean(lX4 | lY4))
     {
     if (Convert.ToBoolean(lResult & 0x40000000))
     {
     lResult = lResult ^ 0xC0000000 ^ lX8 ^ lY8;
     }
     else
     {
     lResult = lResult ^ 0x40000000 ^ lX8 ^ lY8;
     }
     }
     else
     {
     lResult = lResult ^ lX8 ^ lY8;
     }
     AddUnsigned = lResult;
     return AddUnsigned;
     }

     private static long md5_F(long x, long y, long z)
     {
     long md5_F = 0;
     md5_F = (x & y) | ((~x) & z);
     return md5_F;
     }

     private static long md5_G(long x, long y, long z)
     {
     long md5_G = 0;
     md5_G = (x & z) | (y & (~z));
     return md5_G;
     }

     private static long md5_H(long x, long y, long z)
     {
     long md5_H = 0;
     md5_H = (x ^ y ^ z);
     return md5_H;
     }

     private static long md5_I(long x, long y, long z)
     {
     long md5_I = 0;
     md5_I = (y ^ (x | (~z)));
     return md5_I;
     }

     private static void md5_FF(ref long a, long b, long c, long d, long x, long s, long ac)
     {
     a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_F(b, c, d), x), ac));
     a = RotateLeft(a, s);
     a = AddUnsigned(a, b);
     }

     private static void md5_GG(ref long a, long b, long c, long d, long x, long s, long ac)
     {
     a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_G(b, c, d), x), ac));
     a = RotateLeft(a, s);
     a = AddUnsigned(a, b);
     }

     private static void md5_HH(ref long a, long b, long c, long d, long x, long s, long ac)
     {
     a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_H(b, c, d), x), ac));
     a = RotateLeft(a, s);
     a = AddUnsigned(a, b);
     }

     private static void md5_II(ref long a, long b, long c, long d, long x, long s, long ac)
     {
     a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_I(b, c, d), x), ac));
     a = RotateLeft(a, s);
     a = AddUnsigned(a, b);
     }

     private static long[] ConvertToWordArray(string sMessage)
     {
     long[] ConvertToWordArray = null;
     int lMessageLength = 0;
     int lNumberOfWords = 0;
     long[] lWordArray = null;
     int lBytePosition = 0;
     int lByteCount = 0;
     int lWordCount = 0;

     const int MODULUS_BITS = 512;
     const int CONGRUENT_BITS = 448;

     lMessageLength = sMessage.Length;
     lNumberOfWords = (((lMessageLength + ((MODULUS_BITS – CONGRUENT_BITS) / BITS_TO_A_BYTE)) / (MODULUS_BITS / BITS_TO_A_BYTE)) + 1) * (MODULUS_BITS / BITS_TO_A_WORD);
     lWordArray = new long[lNumberOfWords];

     lBytePosition = 0;
     lByteCount = 0;

     while (lByteCount {
     lWordCount = lByteCount / BYTES_TO_A_WORD;
     lBytePosition = (lByteCount % BYTES_TO_A
     _WORD) * BITS_TO_A_BYTE;
     lWordArray[lWordCount] = lWordArray[lWordCount] | LShift(Convert.ToByte(sMessage.Substring(lByteCount, 1).ToCharArray()[0]), lBytePosition);
     lByteCount = lByteCount + 1;
     }

     lWordCount = lByteCount / BYTES_TO_A_WORD;
     lBytePosition = (lByteCount % BYTES_TO_A_WORD) * BITS_TO_A_BYTE;
     lWordArray[lWordCount] = lWordArray[lWordCount] | LShift(0x80, lBytePosition);
     lWordArray[lNumberOfWords – 2] = LShift(lMessageLength, 3);
     lWordArray[lNumberOfWords – 1] = RShift(lMessageLength, 29);
     ConvertToWordArray = lWordArray;

     return ConvertToWordArray;
     }

     private static string WordToHex(long lValue)
     {
     string WordToHex = “”;
     long lByte = 0;
     int lCount = 0;
     for (lCount = 0; lCount {
     lByte = RShift(lValue, lCount * BITS_TO_A_BYTE) & m_lOnBits[BITS_TO_A_BYTE – 1];
     WordToHex = WordToHex + ((“0” + ToHex(lByte)).Substring((“0” + ToHex(lByte)).Length – 2));
     }
     return WordToHex;
     }

     private static string ToHex(long dec)
     {
     string strhex = “”;
     while (dec > 0)
     {
     strhex = tohex(dec % 16) + strhex;
     dec = dec / 16;
     }
     return strhex;
     }

     private static string tohex(long hex)
     {
     string strhex = “”;
     switch (hex)
     {
     case 10: strhex = “a”; break;
     case 11: strhex = “b”; break;
     case 12: strhex = “c”; break;
     case 13: strhex = “d”; break;
     case 14: strhex = “e”; break;
     case 15: strhex = “f”; break;
     default: strhex = hex.ToString(); break;
     }
     return strhex;
     }

     public static string Encrypt(string sMessage, int stype)
     {
     string MD5 = “”;

     for (int i = 0; i {
     m_lOnBits[i] = Convert.ToInt64(Math.Pow(2, i + 1) – 1);
     m_l2Power[i] = Convert.ToInt64(Math.Pow(2, i));
     }

     long[] x = null;
     int k = 0;
     long AA = 0;
     long BB = 0;
     long CC = 0;
     long DD = 0;
     long a = 0;
     long b = 0;
     long c = 0;
     long d = 0;

     const int S11 = 7;
     const int S12 = 12;
     const int S13 = 17;
     const int S14 = 22;
     const int S21 = 5;
     const int S22 = 9;
     const int S23 = 14;
     const int S24 = 20;
     const int S31 = 4;
     const int S32 = 11;
     const int S33 = 16;
     const int S34 = 23;
     const int S41 = 6;
     const int S42 = 10;
     const int S43 = 15;
     const int S44 = 21;

     x = ConvertToWordArray(sMessage);

     a = 0x67452301;
     b = 0xEFCDAB89;
     c = 0x98BADCFE;
     d = 0x10325476;

     for (k = 0; k {
     AA = a;
     BB = b;
     CC = c;
     DD = d;

     md5_FF(ref a, b, c, d, x[k + 0], S11, 0xD76AA478);
     md5_FF(ref d, a, b, c, x[k + 1], S12, 0xE8C7B756);
     md5_FF(ref c, d, a, b, x[k + 2], S13, 0x242070DB);
     md5_FF(ref b, c, d, a, x[k + 3], S14, 0xC1BDCEEE);
     md5_FF(ref a, b, c, d, x[k + 4], S11, 0xF57C0FAF);
     md5_FF(ref d, a, b, c, x[k + 5], S12, 0x4787C62A);
     md5_FF(ref c, d, a, b, x[k + 6], S13, 0xA8304613);
     md5_FF(ref b, c, d, a, x[k + 7], S14, 0xFD469501);
     md5_FF(ref a, b, c, d, x[k + 8], S11, 0x698098D8);
     md5_FF(ref d, a, b, c, x[k + 9], S12, 0x8B44F7AF);
     md5_FF(ref c, d, a, b, x[k + 10], S13, 0xFFFF5BB1);
     md5_FF(ref b, c, d, a, x[k + 11], S14, 0x895CD7BE);
     md5_FF(ref a, b, c, d, x[k + 12], S11, 0x6B901122);
     md5_FF(ref d, a, b, c, x[k + 13], S12, 0xFD987193);
     md5_FF(ref c, d, a, b, x[k + 14], S13, 0xA679438E);
     md5_FF(ref b, c, d, a, x[k + 15], S14, 0x49B40821);
     md5_GG(ref a, b, c, d, x[k + 1], S21, 0xF61E2562);
     md5_GG(ref d, a, b, c, x[k + 6], S22, 0xC040B340);
     md5_GG(ref c, d, a, b, x[k + 11], S23, 0x265E5A51);
     md5_GG(ref b, c, d, a, x[k + 0], S24, 0xE9B6C7AA);
     md5_GG(ref a, b, c, d, x[k + 5], S21, 0xD62F105D);
     md5_GG(ref d, a, b, c, x[k + 10], S22, 0x2441453);
     md5_GG(ref c, d, a, b, x[k + 15], S23, 0xD8A1E681);
     md5_GG(ref b, c, d, a, x[k + 4], S24, 0xE7D3FBC8);
     md5_GG(ref a, b, c, d, x[k + 9], S21, 0x21E1CDE6);
     md5_GG(ref d, a, b, c, x[k + 14], S22, 0xC33707D6);
     md5_GG(ref c, d, a, b, x[k + 3], S23, 0xF4D50D87);
     md5_GG(ref b, c, d, a, x[k + 8], S24, 0x455A14ED);
     md5_GG(ref a, b, c, d, x[k + 13], S21, 0xA9E3E905);
     md5_GG(ref d, a, b, c, x[k + 2], S22, 0xFCEFA3F8);
     md5_GG(ref c, d, a, b, x[k + 7], S23, 0x676F02D9);
     md5_GG(ref b, c, d, a, x[k + 12], S24, 0x8D2A4C8A);
     md5_HH(ref a, b, c, d, x[k + 5], S31, 0xFFFA3942);
     md5_HH(ref d, a, b, c, x[k + 8], S32, 0x8771F681);
     md5_HH(ref c, d, a, b, x[k + 11], S33, 0x6D9D6122);
     md5_HH(ref b, c, d, a, x[k + 14], S34, 0xFDE5380C);
     md5_HH(ref a, b, c, d, x[k + 1], S31, 0xA4BEEA44);
     md5_HH(ref d, a, b, c, x[k + 4], S32, 0x4BDECFA9);
     md5_HH(ref c, d, a, b, x[k + 7], S33, 0xF6BB4B60);
     md5_HH(ref b, c, d, a, x[k + 10], S34, 0xBEBFBC70);
     md5_HH(ref a, b, c, d, x[k + 13], S31, 0x289B7EC6);
     md5_HH(ref d, a, b, c, x[k + 0], S32, 0xEAA127FA);
     md5_HH(ref c, d, a, b, x[k + 3], S33, 0xD4EF3085);
     md5_HH(ref b, c, d, a, x[k + 6], S34, 0x4881D05);
     md5_HH(ref a, b, c, d, x[k + 9], S31, 0xD9D4D039);
     md5_HH(ref d, a, b, c, x[k + 12], S32, 0xE6DB99E5);
     md5_HH(ref c, d, a, b, x[k + 15], S33, 0x1FA27CF8);
     md5_HH(ref b, c, d, a, x[k + 2], S34, 0xC4AC5665);
     md5_II(ref a, b, c, d, x[k + 0], S41, 0xF4292244);
     md5_II(ref d, a, b, c, x[k + 7], S42, 0x432AFF97);
     md5_II(ref c, d, a, b, x[k + 14], S43, 0xAB9423A7);
     md5_II(ref b, c, d, a, x[k + 5], S44, 0xFC93A039);
     md5_II(ref a, b, c, d, x[k + 12], S41, 0x655B59C3);
     md5_II(ref d, a, b, c, x[k + 3], S42, 0x8F0CCC92);
     md5_II(ref c, d, a, b, x[k + 10], S43, 0xFFEFF47D);
    md5_II(refb, c, d, a, x[k + 1], S44, 0x85845DD1);
     md5_II(ref a, b, c, d, x[k + 8], S41, 0x6FA87E4F);
     md5_II(ref d, a, b, c, x[k
     + 15], S42, 0xFE2CE6E0);
     md5_II(ref c, d, a, b, x[k + 6], S43, 0xA3014314);
     md5_II(ref b, c, d, a, x[k + 13], S44, 0x4E0811A1);
     md5_II(ref a, b, c, d, x[k + 4], S41, 0xF7537E82);
     md5_II(ref d, a, b, c, x[k + 11], S42, 0xBD3AF235);
     md5_II(ref c, d, a, b, x[k + 2], S43, 0x2AD7D2BB);
     md5_II(ref b, c, d, a, x[k + 9], S44, 0xEB86D391);

     a = AddUnsigned(a, AA);
     b = AddUnsigned(b, BB);
     c = AddUnsigned(c, CC);
     d = AddUnsigned(d, DD);
     }

     if (stype == 32)
     {
     MD5 = ((((WordToHex(a)) + (WordToHex(b))) + (WordToHex(c))) + (WordToHex(d))).ToLower();
     }
     else
     {
     MD5 = ((WordToHex(b)) + (WordToHex(c))).ToLower();
     }
     return MD5;
     }
     }
    }