Ever since the release of Microsoft .NET 1.0 back in 2002, it has grown to more and more platforms, not only on Microsoft's own platforms but also others. Already in 2003, we saw an open source implementation for BSD variants called DotGNU and its Portable .NET. In 2004, the initial release of Mono came out, whereas a second open source implementation aimed at Linux and Mac OS X. All of a sudden in 2007 with Silverlight, we saw Microsoft targeting multiple platforms themselves with Windows and Mac OS X with an implementation of the CLR and a subset of .NET Framework.

Over the years, we've seen Silverlight come and go, and then Windows Phone 7 came along, which kind of picked up Silverlight and brought it in the future. Back in 2006, before Silverlight came, Microsoft launched Windows Presentation Foundation (WPF)—a new way to perform client development on the Windows stack. This is what Silverlight was built around; a subset of and also what Windows Phone 7 brought with it...