C＃System.ArgumentException：＆＃39;参数不正确。无效的子类型＆＃39;在Windows OCR中

Question

在Windows OCR中可用：https://github.com/Microsoft/Windows-universal-samples/tree/master/Samples/OCR

在OcrCapturedImage.xaml.cs中，我无法弄清楚原因：

private async void ExtractButton_Tapped(object sender, Windows.UI.Xaml.Input.TappedRoutedEventArgs e)
    {

        //Get information about the preview.
        var previewProperties = mediaCapture.VideoDeviceController.GetMediaStreamProperties(MediaStreamType.VideoPreview) as VideoEncodingProperties;
        int videoFrameWidth = (int)previewProperties.Width;
        int videoFrameHeight = (int)previewProperties.Height;

        // Create the video frame to request a SoftwareBitmap preview frame.
        var videoFrame = new VideoFrame(BitmapPixelFormat.Bgra8, videoFrameWidth, videoFrameHeight);

        // Capture the preview frame.
        using (var currentFrame = await mediaCapture.GetPreviewFrameAsync(videoFrame))
        {
            // Collect the resulting frame.
            SoftwareBitmap bitmap = currentFrame.SoftwareBitmap;

            OcrEngine ocrEngine = OcrEngine.TryCreateFromLanguage(ocrLanguage);

            if (ocrEngine == null)
            {
                rootPage.NotifyUser(ocrLanguage.DisplayName + " is not supported.", NotifyType.ErrorMessage);

                return;
            }

            var imgSource = new WriteableBitmap(bitmap.PixelWidth, bitmap.PixelHeight);
            bitmap.CopyToBuffer(imgSource.PixelBuffer);
            PreviewImage.Source = imgSource;

            var ocrResult = await ocrEngine.RecognizeAsync(bitmap);

        }
    }

我收到以下问题：

系统例外

System.ArgumentException：＆＃39;参数不正确。

无效的子类型＆＃39;

这是完整的方法：

-m32

感谢您的帮助