private void VirtualizeItem(VirtualizingFlipViewItem item)
 {
     if (_nextVirtualizingItem != null)
     {
         _virtualizeItemTaskCancellationTokenSource?.Cancel();
         _nextVirtualizingItem.Virtualize();
         _virtualizeItemTask = null;
         _virtualizeItemTaskCancellationTokenSource = null;
     }
     _nextVirtualizingItem = item;
     _virtualizeItemTaskCancellationTokenSource = new CancellationTokenSource();
     _virtualizeItemTask = new Task(ToVirtualizeItem, _virtualizeItemTaskCancellationTokenSource.Token);
     _virtualizeItemTask.Start();
 }
 private async void RealizeItem(VirtualizingFlipViewItem item)
 {
     if (_nextVirtualizingItem == item)
     {
         _virtualizeItemTaskCancellationTokenSource?.Cancel();
         _nextVirtualizingItem = null;
         _virtualizeItemTask = null;
         _virtualizeItemTaskCancellationTokenSource = null;
     }
     await item.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, item.Realize);
 }