public sealed class BankDownloader
    {
        private string _path;
        public bool Controller()
        {
            _path= Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), @"temp.txt");
            return (File.Exists(_path)) ? UpdateFile() : DownloadFile();
        }

        public bool DownloadFile()
        {
            using (var connector = new System.Net.WebClient())
            {
                try
                {
                    var encodedPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData),@"tempEncoded.txt");

                    connector.DownloadFile(@"http://www.nbp.pl/banki_w_polsce/ewidencja/dz_bank_jorg.txt",encodedPath);

                    using (var sw = new StreamWriter(_path))
                    {
                        sw.WriteLine($"{DateTime.Now}\n");
                        sw.WriteLine(File.ReadAllText(encodedPath,Encoding.GetEncoding(852)));
                    }

                    File.Delete(encodedPath);

                    return true;
                }
                catch { return false; }
            }
        }

        public bool UpdateFile()
        {
            if (DateTime.Parse(File.ReadAllLines(_path).First()) >= DateTime.Now.AddDays(-7)) return true;
            RemoveFile();
            return DownloadFile();
        }

        public void RemoveFile()
        {
            File.Delete(_path);
        }
    }