Inheritance: System.Windows.Controls.UserControl
        protected void OpenHelp(string topic, string content)
        {
            double height = LayoutRoot.ActualHeight - 24;
            double width = LayoutRoot.ActualWidth - 24;

            helpPopup.Height = height;
            helpPopup.Width = width;

            var child = helpPopup.Child as HelpView;
            if (child == null)
                child = new HelpView();
            child.Height = height;
            child.Width = width;
            child.Topic = topic;
            child.Content = content;

            helpPopup.Child = child;
            helpPopup.IsOpen = true;
        }