The .NET Assembly target exposes custom visual user objects.

The .NET Assembly target exposes custom visual user objects (CVUOs). When you use the
output assembly in a .NET development environment, the visual objects are available as WPF
user controls that can be added to WPF windows or user controls.

This support is similar to the support for nonvisual objects (NVOs) in .NET assemblies, providing
the same wizard and project painter interface. Functions, events, properties, .NET
properties, instance variables, and indexers are exposed through the Objects tab in the
project painter. You can also provide Visual Studio IntelliSense descriptions for classes
and methods.

In the .NET Assembly Project painter, you can choose to deploy only a CVUO by selecting the
Export only the CVO option in the Objects tab. When you choose this
option, no other elements are exported: to deploy other objects, you must unselect
Export only the CVO first.