PDF is not opened in iOS 13

I am using the following code to open the PDF file in Xamarin.Forms iOS platform. The below code is working fine before updating the Xcode version 11.2, after the update, the PDF document is not viewed, it shows the PDF name and format only in the viewer. Can you please anyone let me know why the PDF is not opened in iOS latest version (13.2).

public class PreviewControllerDS : QLPreviewControllerDataSource
{
    private QLPreviewItem _item;
    public PreviewControllerDS(QLPreviewItem item)
    {
        _item = item;
    }
    public override nint PreviewItemCount(QLPreviewController controller)
    {
        return 1;
    }
    public override IQLPreviewItem GetPreviewItem(QLPreviewController controller, nint index)
    {
        return _item;
    }
}

public class QLPreviewItemBundle : QLPreviewItem
{
    string _fileName, _filePath;    
    public QLPreviewItemBundle(string fileName, string filePath)
    {
        _fileName = fileName;
        _filePath = filePath;
    }

    public override string ItemTitle
    {
        get
        {
            return _fileName;
        }
    } 

    public override NSUrl ItemUrl
    {
        get
        {
            var documents = NSBundle.MainBundle.BundlePath;
            var lib = Path.Combine(documents, _filePath);
            var url = NSUrl.FromFilename(lib);       
            return url;
        }
    }
}

Finally, write the PDF file to the file system and call it like below.

string path = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

string filePath = Path.Combine(path, filename);

FileStream fileStream = File.Open(filePath, FileMode.Create);

stream.Position = 0;

stream.CopyTo(fileStream);

fileStream.Flush();

fileStream.Close();

QLPreviewController qlPreviewController = new QLPreviewController();

QLPreviewItem item = new QLPreviewItemBundle(filename, filePath);

qlPreviewController.DataSource = new PreviewControllerDS(item);

UIApplication.SharedApplication.KeyWindow.RootViewController.PresentViewController(qlPreviewController, true, null);