This extension is part of the Rapid XAML Toolkit.
Install the full toolkit to get the generation functionality and much more.
Use your existing ViewModels or data-models to generate the contents of your XAML files.
Select whole classes, or specific properties and generate XAML from them. You can even drag a ViewModel file onto the XAML editor and have it create the XAML.
It might not be the final XAML you use but it can create the basic UI in seconds.
Once the basic XAML is generated, use the Analysis tools to improve it.