Silverlight - Render controls in background thread

Question

I need to print a screenshot of a silverlight UserControl, which I have tried doing the usual way with PrintDocument, but unfortunately it takes too long and because it has to take place on the UI thread the whole application is locked up for too long. It takes so long because the control contains a grid that needs to be measured and printed over many pages.

So I'm looking for a way to do this without locking up the UI thread. Is there any way I can render these controls again (separately from the originally rendered visible controls) on a background thread? The plan would be to then send those to the PrintDocument, or if that isn't possible to use a WritableBitmap to take screenshots of them.

I've had a quick go already but of course I always get thread affinity issues. Given that I don't want these controls to be visible to the user though I'm hoping there is a way to get around that?

Cheers

Answer 1

You can use WriteableBitmap

Get a reference to the root element that you want to reference. You can use XamlReader if you want to load up the XAML dynamically from an external source if you want. Call it ScreenshotRoot

WriteableBitmap bmp = new WriteableBitmap(ScreenshotRoot.RenderSize.Width, ScreenshotRoot.RenderSize.Height)

bmp.Render(ScreenshotRoot, new MatrixTransform());

bmp.Invalidate();

You should be able to do this in another thread.