public class TrialHelper
  {    //默认密钥向量
    private static byte[] Keys = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };
    /// 

    /// DES加密字符串
    /// 
    /// 待加密的字符串
    /// 加密密钥,要求为8位
    /// 加密成功返回加密后的字符串，失败返回源串
    public static string EncryptDES( string encryptString, string encryptKey = "" )
    {
      try
      {
        if (string.IsNullOrEmpty(encryptKey) || encryptKey.Length < 8)
        {
          encryptKey = "winform01";
        }
        byte[] rgbKey = Encoding.UTF8.GetBytes(encryptKey.Substring(0, 8));
        byte[] rgbIV = Keys;
        byte[] inputByteArray = Encoding.UTF8.GetBytes(encryptString);
        DESCryptoServiceProvider dCSP = new DESCryptoServiceProvider();
        MemoryStream mStream = new MemoryStream();
        CryptoStream cStream = new CryptoStream(mStream, dCSP.CreateEncryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
        cStream.Write(inputByteArray, 0, inputByteArray.Length);
        cStream.FlushFinalBlock();
        return Convert.ToBase64String(mStream.ToArray());
      }
      catch
      {
        return encryptString;
      }
    }
    /// 

    /// DES解密字符串
    /// 
    /// 待解密的字符串
    /// 解密密钥,要求为8位,和加密密钥相同
    /// 解密成功返回解密后的字符串，失败返源串
    public static string DecryptDES( string decryptString, string decryptKey = "" )
    {
      try
      {
        if (string.IsNullOrEmpty(decryptKey) || decryptKey.Length < 8)
        {
          decryptKey = "winform01";
        }
        byte[] rgbKey = Encoding.UTF8.GetBytes(decryptKey.Substring(0, 8));
        byte[] rgbIV = Keys;
        byte[] inputByteArray = Convert.FromBase64String(decryptString);
        DESCryptoServiceProvider DCSP = new DESCryptoServiceProvider();
        MemoryStream mStream = new MemoryStream();
        CryptoStream cStream = new CryptoStream(mStream, DCSP.CreateDecryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
        cStream.Write(inputByteArray, 0, inputByteArray.Length);
        cStream.FlushFinalBlock();
        return Encoding.UTF8.GetString(mStream.ToArray());
      }
      catch
      {
        return decryptString;
      }
    }
    /// 

    /// MD5数据加密
    /// 
    /// 加密字段
    /// 加密后的字符串
    public static string GetMD5( string sDataIn )
    {
      System.Security.Cryptography.MD5CryptoServiceProvider md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
      byte[] bytValue, bytHash;
      bytValue = System.Text.Encoding.UTF8.GetBytes(sDataIn);
      bytHash = md5.ComputeHash(bytValue);
      md5.Clear();
      string sTemp = "";
      for (int i = 0; i < bytHash.Length; i++)
      {
        sTemp += bytHash[i].ToString("x").PadLeft(2, '0');
      }
      return sTemp;
    }
  }

    调用：              

//获取登录信息
        loginRecord.Name = tbName.Text.Trim();
        loginRecord.MD5Pwd = TrialHelper.GetMD5(tbPwd.Password); //保存到数据库MD5加密方式
        loginRecord.Pwd = TrialHelper.EncryptDES(tbPwd.Password);//记住密码des加密方式，保存到本地