The .NET Class Libraries Namespace

The APIs provided by the .NET development platform are organized into a set of hierarchical namespaces with logical names. (This illustration shows a few of the more important classes.) This design is in stark contrast to the Win32 API, which is simply a very long list of function names that, at best, could be arranged in alphabetical order. Having a hierarchy enables developers to locate desired functions much more quickly.

In addition to providing an organizational framework for APIs, the hierarchy segments the APIs into namespaces, allowing new APIs to be added without fear of conflicting with existing APIs in other parts of the hierarchy.

The classes build on the base classes (bottom) in the System hierarchy, which include such capabilities as text processing (System.Text), Network access (System.Net), and storing lists and other collections of data (System.Collections).

On top of those base classes are more complex classes, such as Data access (System.Data), which include ADO.NET and XML processing (System.Xml).