This article presents a behavior that can be used to attach properties to a bound class.
This article explains a simpler way of attaching adorners by using a WPF behavior class
An implementation of a numeric on-screen keyboard using attached behaviors in WPF
Enable binding of Enum to ComboBox, a searchable TreeView control and a Windows Form style TreeView with the help of Attached properties.
Implementating Attached Properties and Bindings outside of WPF, in plain C#