Most of the classes in the .NET Framework version 2.0 are unchanged in3.0/3.5. The key differences for .NET 3.0 are new libraries that offercompletely new sets of functionality. There are four main components:

Windows Presentation Foundation (WPF) is a next-generation presentationsystem for building Windows client applications with visually stunninguser experiences. With WPF, you can create a wide range of bothstandalone and browser-hosted applications. Some examples are Yahoo Messanger.
The core of WPF is a resolution-independent and vector-based renderingengine that is built to take advantage of modern graphicshardware. WPF extends the core with a comprehensive set ofapplication-development features that include Extensible ApplicationMarkup Language (XAML), controls, data binding, layout, 2-D and 3-Dgraphics, animation, styles, templates, documents, media, text, andtypography. WPF is included in the Microsoft .NET Framework, so you canbuild applications that incorporate other elements of the .NETFramework class library.
To support some of the more powerful WPF capabilities and to simplifythe programming experience, WPF includes additional programmingconstructs that enhance properties and events: dependency properties and routed events.

WPF offers additional programming enhancements for Windows clientapplication development. One obvious enhancement is the ability todevelop an application using both markup and code-behind,an experience that ASP.NET developers should be familiar with. Yougenerally use Extensible Application Markup Language (XAML) markup toimplement the appearance of an application while using managedprogramming languages (code-behind) to implement its behavior. Thisseparation of appearance and behavior has the following benefits:

• Development and maintenance costs arereduced because appearance-specific markup is not tightly coupled withbehavior-specific code.

• Development is more efficientbecause designers can implement an application's appearancesimultaneously with developers who are implementing the application'sbehavior.

• Multiple design tools can be used toimplement and share XAML markup, to target the requirements of theapplication development contributors; Microsoft Expression Blend provides an experience that suits designers, while Visual Studio 2005 targets developers.

• Globalization and localization for WPF applications is greatly simplified