private void MainWindow_OnLoaded(object sender, RoutedEventArgs e)
        {
            _connectionString = ConfigurationManager.ConnectionStrings["connectToTTN"].ConnectionString;
            var rk = Registry.CurrentUser.OpenSubKey("PostWatcher");
            bool isLogined = true;
         
            if (rk == null)
            {
                rk = Registry.CurrentUser.CreateSubKey("PostWatcher");
                isLogined = false;
            }
            else
                if (rk.GetValue("API key") == null)
                    isLogined = false;

            if (!isLogined)
            {
                var newWindwowApIkey = new APIkey();
                newWindwowApIkey.ShowDialog();
                _apiKey = (string)rk.GetValue("API key");

                OpenLoader("InternetDocument", "getDocumentList", null);
            }

            _apiKey = (string)rk.GetValue("API key");

            //Bad realization
            //Refresh all Libraries of NovaPoshta.
            OpenLoader("InternetDocument", "getDocumentList", null);
        }
        private void menuChangeAPIkey_OnClick(object sender, RoutedEventArgs e)
        {
            var newWindow = new APIkey();
            newWindow.ShowDialog();
            var rk = Registry.CurrentUser.OpenSubKey("PostWatcher");
            _apiKey = (string)rk.GetValue("API key");

        }