In order to write practical code, you need to know quite a bit about the classes you have to work with. That means acquiring a thorough knowledge of the core class libraries that ship with Silverlight. Silverlight includes a subset of the classes from the full .NET Framework. Although it would be impossible to cram the entire .NET Framework into Silverlight—after all, it’s a 4MB download that needs to support a variety of browsers and operating systems—Silverlight includes a remarkable amount of functionality. The Silverlight version of the .NET Framework is simplified in two ways. First, it doesn’t provide the sheer number of types you’ll find in the full .NET Framework. Second, the classes that it does include often don’t provide the full complement of constructors, methods, properties, and events. Instead, Silverlight keeps only the most practical members of the most important classes, which leaves it with enough functionality to create surprisingly compelling code.