Silverlight 4 is a new technology from Microsoft designed to develop rich Web applications, or applications with a "rich" interface. The main characteristics of Silverlight applications are intensive use of graphics, animation, working with media files, as well as effective interaction with data and server components. At the same time, the developer has the ability not only to use managed programming languages ​ ​ (C #, VB.NET) to develop Silverlight applications, but also to access most of the benefits available in the .NET Framework. If we take into account that the process of developing Silverlight applications is closely integrated into Visual Studio, then we can say that using Silverlight will not cause difficulties for existing .NET developers. This book can be useful for everyone who decided to study Silverlight 4 and already has a general knowledge of developing applications on the .NET platform.