A new control “XAMLHost” was added to the Standard Controls in the Application Designer, as shown below. This control can be dropped onto any container control (Group Box, Tab page, or Panel). You can set the Anchoring and/or Docking as desired.
Clicking on the ellipsis button to the right of the attribute “XAML” in the Properties grid will open the XAML Editor (shown below) where you can edit XAML code. Alternatively, XAML developed using Visual Studio or Expression Blend can be directly pasted in, as longs it adheres to the standards.