private void _browser_OnDocumentCompleted(object sender, GeckoDocumentCompletedEventArgs geckoDocumentCompletedEventArgs) { Debug.WriteLine("_browser_OnDocumentCompleted ({0})", Thread.CurrentThread.ManagedThreadId); var order = (ThumbnailOrder)((GeckoWebBrowser)sender).Tag; order.Done = true; if (order.WaitHandle != null) order.WaitHandle.Set(); }