WPF/WinForms/GDI interop: converting a WriteableBitmap to a System.Drawing.Image?

Question

How can I convert a WPF WriteableBitmap object to a System.Drawing.Image?

My WPF client app sends bitmap data to a web service, and the web service needs to construct a

Answer 1

The question is for WPF, and Pixels does not appear to be a property of WriteableBitmap. Some of the answers here point to SilverLight articles, so I suspect this might be a difference between WPF and SilverLight.