/// <summary>
    /// DEC 加密过程
    /// </summary>
    /// <param name="pToEncrypt">被加密的字符串</param>
    /// <param name="sKey">密钥（只支持8个字节的密钥）</param>
    /// <returns>加密后的字符串</returns>
    public static string Encrypt(string pToEncrypt, string sKey)
    {
        //访问数据加密标准(DES)算法的加密服务提供程序 (CSP) 版本的包装对象
        DESCryptoServiceProvider des = new DESCryptoServiceProvider();
        des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);　//建立加密对象的密钥和偏移量
        des.IV = ASCIIEncoding.ASCII.GetBytes(sKey);　 //原文使用ASCIIEncoding.ASCII方法的GetBytes方法
        byte[] inputByteArray = Encoding.Default.GetBytes(pToEncrypt);//把字符串放到byte数组中
        MemoryStream ms = new MemoryStream();//创建其支持存储区为内存的流　
        //定义将数据流链接到加密转换的流
        CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);
        cs.Write(inputByteArray, 0, inputByteArray.Length);
        cs.FlushFinalBlock();
        //上面已经完成了把加密后的结果放到内存中去
        StringBuilder ret = new StringBuilder();
        foreach (byte b in ms.ToArray())
        {
            ret.AppendFormat("{0:X2}", b);
        }
        ret.ToString();
        return ret.ToString();
    }
    /// <summary>
    /// DEC 解密过程
    /// </summary>
    /// <param name="pToDecrypt">被解密的字符串</param>
    /// <param name="sKey">密钥（只支持8个字节的密钥，同前面的加密密钥相同）</param>
    /// <returns>返回被解密的字符串</returns>
    public static string Decrypt(string pToDecrypt, string sKey)
    {
        DESCryptoServiceProvider des = new DESCryptoServiceProvider();
        byte[] inputByteArray = new byte[pToDecrypt.Length / 2];
        for (int x = 0; x < pToDecrypt.Length / 2; x++)
        {
            int i = (Convert.ToInt32(pToDecrypt.Substring(x * 2, 2), 16));
            inputByteArray[x] = (byte)i;
        }
        des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);　//建立加密对象的密钥和偏移量，此值重要，不能修改
        des.IV = ASCIIEncoding.ASCII.GetBytes(sKey);
        MemoryStream ms = new MemoryStream();
        CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);
        cs.Write(inputByteArray, 0, inputByteArray.Length);
        cs.FlushFinalBlock();
        //建立StringBuild对象，createDecrypt使用的是流对象，必须把解密后的文本变成流对象
        StringBuilder ret = new StringBuilder();
        return System.Text.Encoding.Default.GetString(ms.ToArray());
    }

    /// <summary>
    /// 密码加密过程
    /// </summary>
    /// <param name="pwd">密码</param>
    /// <returns>加密后的字符串</returns>
    public static string pwdEncrypt(string pwd)
    {
        string pwdJm = Encrypt(pwd, "ABCQiS88");
        return pwdJm;
    }
    /// <summary>
    /// 密码加密过程
    /// </summary>
    /// <param name="pwd">密码</param>
    /// <returns>加密后的字符串</returns>
    public static string pwdDecrypt(string pwd)
    {
        string pwdJm = Decrypt(pwd, "ABCQiS88");
        return pwdJm;
    }

一般处理程序调用：String txtPwdD5 = sqlhelper.pwdEncrypt(admin_Password);