When building XAML applications in WPF, Silverlight, Windows 8, or Windows Phone, you will often find yourself saying, "If only this element had the ability to do X, Y, or Z from the XAML!" Behaviors are a pattern of extensibility in XAML that allow you to add capabilities to existing XAML elements yourself, even if you don’t have access to the source code of the elements you are trying to extend. You can extend elements that are part of the core XAML libraries, 3rd party controls, or even your own controls all using a set of pre-built behaviors or by building your own custom behaviors. In this course, you will learn what behaviors are all about, how they are built and work, and why you want to use them. You'll learn how to get highly productive quickly by using the pre-built Blend SDK and Behaviors SDK built-in behaviors, as well as how to build custom behaviors from scratch for more specialized scenarios. You will see how the same set of skills and built-in behaviors will allow you to apply the same kinds of functionality across the different XAML stacks of WPF, Windows 8, Windows Phone, and Silverlight.