VS_XAML_TYPE
Mark a Extensible Application Markup Language (XAML) source file as a different type than the default Page. The most common usage would be to set the default App.xaml file as ApplicationDefinition.
© 2000–2020 Kitware, Inc. and Contributors
Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.17/prop_sf/VS_XAML_TYPE.html