Xamarin - How to get a screenshot and save it on disk using xamarin mac?

I'm trying to grab a screenshot and save it on disk using Xamarin and C# on Mac. I wrote the code below:

public static void TakeScreenshotAndSaveToDisk(string path)
    {
        var fullScreenBounds = NSScreen.MainScreen.Frame;
        IntPtr ptr = CGWindowListCreateImage(fullScreenBounds, CGWindowListOption.OnScreenAboveWindow, 0, CGWindowImageOption.Default);
        var cgImage = new CGImage(ptr);
        var fileURL = new NSUrl(path, false);
        var imageDestination = CGImageDestination.Create(new CGDataConsumer(fileURL), UTType.PNG, 1);
        imageDestination.AddImage(cgImage);
        imageDestination.Close();
        imageDestination.Dispose();
        fileURL.Dispose();
        cgImage.Dispose();
    }

The method executes and the file appears at the correct location. If I try to open it, it will show blank. If I click "Get Info" on the file it will not show a preview. After I close my app, the image can be opened and "Get Info" shows the preview.

What am I doing wrong here? It seems to me that the resources are not released even though I call Dispose() on the objects.

Thanks.