string JiaMi = Md5Encrypt(LoginPwd);
    string JieMi = Md5Decrypt(JiaMi);

    #region MD5加密
    /// <summary>   
    /// MD5加密   
    /// </summary>   
    /// <param name="strSource">需要加密的字符串</param>   
    /// <returns>MD5加密后的字符串</returns>   
    public static string Md5Encrypt(string strSource)
    {
      //把字符串放到byte数组中   
      byte[] bytIn = System.Text.Encoding.Default.GetBytes(strSource);
      //建立加密对象的密钥和偏移量       
      byte[] iv = { 102, 16, 93, 156, 78, 4, 218, 32 };//定义偏移量   
      byte[] key = { 55, 103, 246, 79, 36, 99, 167, 3 };//定义密钥   
      //实例DES加密类   
      DESCryptoServiceProvider mobjCryptoService = new DESCryptoServiceProvider();
      mobjCryptoService.Key = iv;
      mobjCryptoService.IV = key;
      ICryptoTransform encrypto = mobjCryptoService.CreateEncryptor();
      //实例MemoryStream流加密密文件   
      System.IO.MemoryStream ms = new System.IO.MemoryStream();
      CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Write);
      cs.Write(bytIn, 0, bytIn.Length);
      cs.FlushFinalBlock();
      return System.Convert.ToBase64String(ms.ToArray());
    }
    #endregion


    #region MD5解密
    /// <summary>   
    /// MD5解密   
    /// </summary>   
    /// <param name="Source">需要解密的字符串</param>   
    /// <returns>MD5解密后的字符串</returns>   
    public static string Md5Decrypt(string Source)
    {
      //将解密字符串转换成字节数组   
      byte[] bytIn = System.Convert.FromBase64String(Source);
      //给出解密的密钥和偏移量，密钥和偏移量必须与加密时的密钥和偏移量相同   
      byte[] iv = { 102, 16, 93, 156, 78, 4, 218, 32 };//定义偏移量   
      byte[] key = { 55, 103, 246, 79, 36, 99, 167, 3 };//定义密钥   
      DESCryptoServiceProvider mobjCryptoService = new DESCryptoServiceProvider();
      mobjCryptoService.Key = iv;
      mobjCryptoService.IV = key;
      //实例流进行解密   
      System.IO.MemoryStream ms = new System.IO.MemoryStream(bytIn, 0, bytIn.Length);
      ICryptoTransform encrypto = mobjCryptoService.CreateDecryptor();
      CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Read);
      StreamReader strd = new StreamReader(cs, Encoding.Default);
      return strd.ReadToEnd();
    }
    #endregion