make class instance in xaml
--- https://subscription.packtpub.com/book/application_development/9781849686228/1/ch01lvl1sec09/creating-custom-type-instances-in-xaml
<Window x:Class="CH01.CustomTypes.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:CH01.CustomTypes">
...
<Button FontSize="20">
<local:Book Name="Windows Internals"
Author="Mark Russinovich" Price="40"
YearPublished="2009" />
</Button>