There is a specific Winforms sample for the facebook SDK available here: Facebook Sample using Facebook C# SDK with WinForms

This sample demonstrates the use of Facebook C# SDK v6 as a WinForms sample.

Note: This sample does not necessarily demonstrate the best use but rather features of using Facebook C# SDK on a desktop app. It is always recommended to use asynchronous (XAsync or XTaskAsync) methods rather then the synchronous methods. XTaskAsync methods are preferred over XAsync methods.