public async void SaveChartOne()
 {
     if (App.StatisticsData != null)
     {
         await fileService.SaveChartAsPNGAsync(App.StatisticsData.ChartOne, "ChartOne");
     }
     else
     {
         await new Windows.UI.Popups.MessageDialog("Can't save the chart - no statistical data.").ShowAsync();
     }
 }