The .NET Framework Class Library

The .NET Framework class library defines a collection of reusable types that integrate with the CLR. It is object-oriented, providing types and classes from which a developer's code can derive functionality. For example, it defines a Web service class, System.Web.Services.WebService, from which a Web service can easily be created through derivation. Similarly, many common programming tasks and artifacts are implemented in the framework to improve productivity and ease the task of the developer.

The classes in the class library are divided logically into namespaces, which will look very familiar if one is used to using Java packages. These namespaces organize the many thousands of available classes into hierarchies that separate them according to their functionality. For example, if developing Windows applications, the classes are in the top level System.Windows.Forms namespace, and for Web applications they are organized under the System.Web namespace. For interoperability, Web services are at the heart of the .NET Framework, so a System.XML collection of namespaces is available and is separate from System.Web.Servicesas Web services may be consumed by Windows applications. It is also logically separated as XML is decoupled from Web and Windows applications in that it is a useful data management technology that is separate and independent from Web or Windows applications that may use it.

A comprehensive overview of the .NET Framework namespaces is beyond the scope of this book, but there are many good references, including the Microsoft Developer Network (http://msdn.microsoft.com).