public static void ShowAsync(string header, string content)
 {
     Application.Current.Dispatcher.BeginInvoke((Action) delegate
     {
         var dialog = new ErrorDialog(header, content);
         if (Settings.mainWindow != null)
         {
             dialog.Owner = Settings.mainWindow;
             dialog.WindowStartupLocation = WindowStartupLocation.CenterOwner;
         }
         else
         {
             dialog.WindowStartupLocation = WindowStartupLocation.CenterScreen;
         }
         dialog.ShowDialog();
     });
 }