This is the Silverlight Add-in Extensibility Custom Support API Reference. 

Use this reference together with the UFT WPF and Silverlight Add-in Extensibility Developer Guide. The developer guide contains full details on how to develop support for custom Silverlight controls. In addition to creating configuration files, you must also develop a custom server for every control that you want to support. The custom server DLL runs in the context of the application and interfaces between UFT and the custom control.

For a brief overview of what you implement in a custom server, see Custom Support API References.