我要做一个加密记事本的小程序  要把编辑完成后的.txt文件 加密成未知程序 如何获取文件名并对名称和后缀名进行异或运算？

//默认密钥向量
private static byte[] Keys = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };
//加密成功返回加密后的字符串,失败返回源串
public static string Encode(string encryptString, string encryptKey)
{
       encryptKey = encryptKey.PadRight(8, ' ');
       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());
   }
//解密成功返回解密后的字符串,失败返源串
public static string Decode(string decryptString, string decryptKey)
{
      try
      {
             decryptKey = decryptKey.PadRight(8, ' ');
             byte[] rgbKey = Encoding.UTF8.GetBytes(decryptKey);
             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 "";
            }
}