关于uwp用win2d DrawImage的问题

Question

我按照例子写了一段，但是到了DrawImage的时候总是报错，错误是

An exception of type 'System.ObjectDisposedException' occurred in test.exe but was not handled in user code

Additional information: 该对象已关闭。 (Exception from HRESULT: 0x80000013)

private async void cc_Draw(CanvasControl sender, CanvasDrawEventArgs args)
{
            Rect rect = new Rect(0, 0, 1024, 768);
            FileOpenPicker filePicker = new FileOpenPicker();
            filePicker.ViewMode = PickerViewMode.Thumbnail;
            filePicker.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
            filePicker.FileTypeFilter.Add("*");
            StorageFile file = await filePicker.PickSingleFileAsync();
            var stream = await file.OpenAsync(FileAccessMode.ReadWrite);
            var b = await CanvasBitmap.LoadAsync(sender, stream);             
            args.DrawingSession.DrawImage(b, rect);
}

b已经被赋值，而且是正确的，就是我打开了了一张1024*768图片，但是一执行args.DrawingSession.DrawImage(b, rect);
就会报错

Answer 1

请问有人知道吗？

Answer 2

自己写了个例子，能用

https://code.msdn.microsoft.com/UwpWin2dSimpleDemo-901c020d