asp.net中实现MD5加密、解密的方法

/*用法
 protected void Page_Load(object sender, EventArgs e)
    {
        //加密
        this.Title = CEncrypt.DesEncrypt("pwd", CEncrypt.Key);
        this.Title += CEncrypt.DesDecrypt(this.Title, CEncrypt.Key);
        Response.Write(CEncrypt.DesDecrypt("gAYyhdLQunc=", CEncrypt.Key));
    }
 */
using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;
using System.Web;

namespace YD.Common
{
    /// <summary>
    /// 加密码类
    /// </summary>
    public class CEncrypt
    {
        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="inputString"></param>
        /// <returns></returns>
        public static string DesEncrypt(string inputString)
        {
            return DesEncrypt(inputString, Key);
        }
        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="inputString"></param>
        /// <returns></returns>
        public static string DesDecrypt(string inputString)
        {
            return DesDecrypt(inputString, Key);
        }
        /// <summary>
        /// 密匙
        /// </summary>
        private static string Key
        {
            get
            {
                return "hongye10";
            }
        }
        /// <summary>
        /// 加密字符串
        /// 注意:密钥必须为８位
        /// </summary>
        /// <param name="strText">字符串</param>
        /// <param name="encryptKey">密钥</param>
        /// <param name="encryptKey">返回加密后的字符串</param>
        public static string DesEncrypt(string inputString, string encryptKey)
        {
            byte[] byKey = null;
            byte[] IV = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };
            try
            {
                byKey = System.Text.Encoding.UTF8.GetBytes(encryptKey.Substring(0, 8));
                DESCryptoServiceProvider des = new DESCryptoServiceProvider();
                byte[] inputByteArray = Encoding.UTF8.GetBytes(inputString);
                MemoryStream ms = new MemoryStream();
                CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(byKey, IV), CryptoStreamMode.Write);
                cs.Write(inputByteArray, 0, inputByteArray.Length);
                cs.FlushFinalBlock();
                return Convert.ToBase64String(ms.ToArray());
            }
            catch (System.Exception error)
            {
                //return error.Message;
                return null;
            }
        }
        /// <summary>
        /// 解密字符串
        /// </summary>
        /// <param name="this.inputString">加了密的字符串</param>
        /// <param name="decryptKey">密钥</param>
        /// <param name="decryptKey">返回解密后的字符串</param>
        public static string DesDecrypt(string inputString, string decryptKey)
        {
            byte[] byKey = null;
            byte[] IV = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };
            byte[] inputByteArray = new Byte[inputString.Length];
            try
            {
                byKey = System.Text.Encoding.UTF8.GetBytes(decryptKey.Substring(0, 8));
                DESCryptoServiceProvider des = new DESCryptoServiceProvider();
                inputByteArray = Convert.FromBase64String(inputString);
                MemoryStream ms = new MemoryStream();
                CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(byKey, IV), CryptoStreamMode.Write);
                cs.Write(inputByteArray, 0, inputByteArray.Length);
                cs.FlushFinalBlock();
                System.Text.Encoding encoding = new System.Text.UTF8Encoding();
                return encoding.GetString(ms.ToArray());
            }
            catch (System.Exception error)
            {
                //return error.Message;
                return null;
            }
        }
    }
}