/// <summary>
      /// Open file for playing
      /// </summary>
      /// <param name="sender"></param>
      /// <param name="e"></param>
      private void MenuOpenFile_OnClick(object sender, RoutedEventArgs e) {
         try {
            var objDialog = new OpenFileDialog() {
               Filter = "Media files| *.mp4; *.avi; *.mp3; *.wav; *.pl"
            };
            bool? result = objDialog.ShowDialog();
            if(result == true) {
               var objFileInfo = new FileInfo(objDialog.FileName);
               //rewrite current play list
               _PlayList = new PlayList();

               //if we opened playlist
               if(objFileInfo.Extension == ".pl") {
                  _PlayList.Open(objDialog.FileName);
                  UpdatePlayListView();
               }
               else {
                  //if we opened standart media file
                  var objMediaFile = new MediaFile(objFileInfo);
                  _PlayList.MediaFiles.Add(objMediaFile);
                  ListBoxPlayList.Items.Add(objMediaFile);
               }
               ListBoxPlayList.SelectedIndex = 0;
               ListBoxPlayList_OnMouseDoubleClick(sender, null);
            }
         }
         catch(Exception ex) {
            MessageBox.Show(ex.Message);
         }
      }
 private void Window_Loaded(object sender, RoutedEventArgs e) {
    _Timer = new DispatcherTimer { Interval = new TimeSpan(0, 0, 1) };
    _Timer.Tick += new EventHandler(dispatcherTimer_Tick);
    _PlayList = new PlayList();
    sliderVolume.Value = mediaElement.Volume;
 }