If you want the latest tips and tricks on maximizing your app compatibility and
optimizing your code, sign up for “Building Apps for Windows Phone 8.1 Jump
Start,” a three-day (April 29, 30, and May 1) event led by seasoned experts.
Learn to create universal app projects in Visual Studio that share a high
percentage of code and that target both Windows and Windows Phone. Find out
about new features, get code samples, and learn how to program the new Windows
Runtime APIs that are available to both Windows Store apps and to Windows
Silverlight apps. This is a great course for .NET and Silverlight app
developers who want to design and build Windows Phone 8.1 apps using XAML and
C#.  No prior experience with developing Windows Phone 8 apps is required.
Register here.