.Net Class Library

The .NET Framework class library is a collection of reusable types that tightly integrate with the common language runtime. The class library is object oriented, providing types from which your own managed code can derive functionality. This not only makes the .NET Framework types easy to use, but also reduces the time associated with learning new features of the .NET Framework. In addition, third-party components can integrate seamlessly with classes in the .NET Framework.
For example, the .NET Framework collection classes implement a set of interfaces that you can use to develop your own collection classes. Your collection classes will blend seamlessly with the classes in the .NET Framework.
As you would expect from an object-oriented class library, the .NET Framework types enable you to accomplish a range of common programming tasks, including tasks such as string management, data collection, database connectivity, and file access. In addition to these common tasks, the class library includes types that support a variety of specialized development scenarios. For example, you can use the .NET Framework to develop the following types of applications and services:

• Console applications. 
• Windows GUI applications (Windows Forms).
• Windows Presentation Foundation (WPF) applications. 
• ASP.NET applications. 
• Windows services. 
• Service-oriented applications using Windows Communication Foundation (WCF). 
• Workflow-enabled applications using Windows Workflow Foundation (WF).

For example, the Windows Forms classes are a comprehensive set of reusable types that vastly simplify Windows GUI development. If you write an ASP.NET Web Form application, you can use the Web Forms classes.

The .NET Framework includes classes, interfaces, and value types that expedite and optimize the development process and provide access to system functionality. To facilitate interoperability between languages, most .NET Framework types are CLS-compliant and can therefore be used from any programming language whose compiler conforms to the common language specification (CLS).
The .NET Framework types are the foundation on which .NET applications, components, and controls are built. The .NET Framework includes types that perform the following functions:

• Represent base data types and exceptions.
• Encapsulate data structures.
• Perform I/O.
• Access information about loaded types.
• Invoke .NET Framework security checks.
• Provide data access, rich client-side GUI, and server-controlled, client-side GUI.

The .NET Framework provides a rich set of interfaces, as well as abstract and concrete (non-abstract) classes. You can use the concrete classes as is or, in many cases, derive your own classes from them. To use the functionality of an interface, you can either create a class that implements the interface or derive a class from one of the .NET Framework classes that implements the interface.