Microsoft has just released Silverlight 4 based facebook client for both Windows and Mac OS X. Back in April last year, Microsoft showed off a proof of concept facebook client which was made using facebook’s Open Stream API on Silverlight but unfortunately that never saw the light of the day. After a long wait, they have finally released a fully working client for users running Windows and OS X – with full capability to run it out-of-the-browser.

Microsoft today has released an update to its Software Development Kit (SDK) for the most popular social networking site, Facebook. With Microsoft SDK for Facebook Platform 3.0, developers can build rich Facebook applications using Silverlight, WPF (Windows Presentation Foundation), ASP.NET, ASP.NET MVC and Windows Forms. The SDK contains samples, controls, templates, and help documentation for implementing a simple Facebook Connect functionality, to a fully functional desktop, mobile or a web application. According to a Microsoft spokesperson: “the goal is to enable .NET developers to quickly and easily leverage the various features of the Facebook Platform.”.