public void OnTwitterCommand(object arg)
        {
            TwitterService twitterService = new TwitterService();

            if (twitterService.AuthenticationRequired())
            {
                if (_windowService == null)
                {
                    _windowService = new WindowService();
                }

                _windowService.CreateWindow(new TwitterLoginVM());
            }
            else
            {
                string message;

                if (_currentMedia.GetType() == typeof(Music))
                {
                    if ((_currentMedia as Music).Artists != null)
                    {
                        message = "Entrain d'écouter " + _currentMedia.Name + " de " + (_currentMedia as Music).Artists + " sur #MyWindowsMediaPlayer";
                    }
                    else
                    {
                        message = "Entrain d'écouter " + _currentMedia.Name + " sur #MyWindowsMediaPlayer";
                    }
                }
                else if (_currentMedia.GetType() == typeof(Video))
                {
                    message = "Entrain de regarder " + _currentMedia.Name + " sur #MyWindowsMediaPlayer";
                }
                else
                {
                    message = "Entrain de lire le média " + _currentMedia.Name + " sur #MyWindowsMediaPlayer";
                }

                if (twitterService.SendTweet(message) == false)
                {
                    _twitterCommand.RaiseCanExecuteChanged();
                    _twitterPopup.Message = "Erreur : " + twitterService.LastError;
                    _twitterPopup.Show(5);
                    System.Diagnostics.Debug.WriteLine("Unable to send tweet: " + twitterService.LastError);
                }
                else
                {
                    _currentMedia.Tweeted = true;
                    _twitterCommand.RaiseCanExecuteChanged();
                    _twitterPopup.Message = "Votre tweet a bien été envoyé !";
                    _twitterPopup.Show(3);
                }
            }
        }