/// 
  /// 加密／解密工具  /// 
  public class CEncoder  {      const string key = "a3f3bc6d43e7f10d";      /// 
      /// 字符串加密.由DESCryptoServiceProvider对象加密      /// 
      public static string Encode(string str)      {          try          {              DESCryptoServiceProvider provider = new DESCryptoServiceProvider();              provider.Key = Encoding.ASCII.GetBytes(key.Substring(0, 8));              provider.IV = Encoding.ASCII.GetBytes(key.Substring(0, 8));              byte[] bytes = Encoding.Default.GetBytes(str);              MemoryStream stream = new MemoryStream();              CryptoStream stream2 = new CryptoStream(stream, provider.CreateEncryptor(), CryptoStreamMode.Write);              stream2.Write(bytes, 0, bytes.Length);              stream2.FlushFinalBlock();              StringBuilder builder = new StringBuilder();              foreach (byte num in stream.ToArray())              {                  builder.AppendFormat("{0:X2}", num);              }              stream.Close();              return builder.ToString();          }          catch          {              return string.Empty;          }      }      /// 
      /// 字符串解密.由DESCryptoServiceProvider对象解密      /// 
      public static string Decode(string str)      {          try          {              DESCryptoServiceProvider provider = new DESCryptoServiceProvider();              provider.Key = Encoding.ASCII.GetBytes(key.Substring(0, 8));              provider.IV = Encoding.ASCII.GetBytes(key.Substring(0, 8));              byte[] buffer = new byte[str.Length / 2];              for (int i = 0; i < (str.Length / 2); i++)              {                  int num2 = Convert.ToInt32(str.Substring(i * 2, 2), 0x10);                  buffer[i] = (byte)num2;              }              MemoryStream stream = new MemoryStream();              CryptoStream stream2 = new CryptoStream(stream, provider.CreateDecryptor(), CryptoStreamMode.Write);              stream2.Write(buffer, 0, buffer.Length);              stream2.FlushFinalBlock();              stream.Close();              return Encoding.Default.GetString(stream.ToArray());          }          catch          {              return string.Empty;          }      }      private static int PREFIX_LEN = 6;      /// 
      /// RETURN [PREFIX]+STRING      /// 
      public static string Encode(string source, bool genPrefix)      {          if (source == string.Empty) return "";          if (genPrefix)              return GetPrefix(PREFIX_LEN) + CEncoder.Encode(source);          else              return CEncoder.Encode(source);      }      /// 
      /// [PREFIX]STRING-->STRING      /// 
      public static string Decode(string source, bool hasPrefix)      {          if (source == string.Empty) return "";          if (source.Length <= PREFIX_LEN || !hasPrefix)              return Decode(source);          else if (hasPrefix)              return Decode(source.Substring(PREFIX_LEN, source.Length - PREFIX_LEN));          else              return Decode(source);      }      /// 
      /// MD5加密，Use object MD5,返回16字符串      /// 
      public static string encryptMD5(string content)      {          string retContent = "";          MD5 md5 = MD5.Create();          // 加密后是一个字节类型的数组           byte[] s = md5.ComputeHash(Encoding.Unicode.GetBytes(content));          // 通过使用循环，将字节类型的数组转换为字符串，此字符串是常规字符格式化所得           for (int i = 0; i < s.Length; i++)          {              // 将得到的字符串使用十六进制类型格式。格式后的字符是小写的字母，              //如果使用大写（X）则格式后的字符是大写字符               retContent = retContent + s[i].ToString("X");          }          return retContent;      }      /// 
      /// MD5不可逆加密.use MD5CryptoServiceProvider      /// 
      public static string GenerateMD5Hash(string input)      {          MD5CryptoServiceProvider md5Hasher = new MD5CryptoServiceProvider();          byte[] data = md5Hasher.ComputeHash(Encoding.Default.GetBytes(input));          StringBuilder sBuilder = new StringBuilder();          for (int i = 0; i < data.Length; i++)          {              sBuilder.Append(data[i].ToString("x2"));          }          return sBuilder.ToString();      }      /// 
      /// 密码头      /// 
      public static string GetPrefix(int bit)      {          //A-Z 0-9          string chars = "0A1D30A4B5C006D72C8E92030F506E7E02F1A0D023B3B40C5E180D6F4D5E6F";          string ret = "";          if (bit < 1) bit = PREFIX_LEN;          for (int i = 1; i <= bit; i++)          {              int n = GetRandomNum(chars.Length - 2);              ret = ret + chars.Substring(n, 1);          }          return ret;      }      /// 
      /// 取随机数      /// 
      /// 最大数      /// 
           public static int GetRandomNum(int maxValue)      {          Random seed = new Random();          Random randomNum = new Random();          Thread.Sleep(20);          return randomNum.Next(1, maxValue);      }  }