How can I show a wpf control over a WPF Browser Control

Hi,

Can you please advise how to show a wpf control over a WPF Browser Control. I could see an option will be to use WPF PopUps.  Is there any other solution for this. 

Also can you please advise any known issue while using Popups for this. One issue I could see is  Black background if not content is rendered there.Is there any other way of showing web pages dynamically other than using web browser control in wpf? I am using an XBAP Application.

Thanks in advance