About Microsoft .NET Framework 3.0

The Microsoft .NET Framework version 3.0 (formerly known as WinFX) is the new managed-code programming model for Windows. It combines the power of .NET Framework 2.0 with new technologies for building applications that have a visually compelling user experience, seamless communication across technology boundaries, and support for a wide range of business processes.

All of the classes that represent the new components (WPF, WF, WCF, and CardSpace) are part of the System namespace. The core classes of the .NET platform, such as the common language runtime (CLR) and base class libraries (BCL) remain as they are in .NET Framework 2.0.



How .NET Framework 3.0 Relates to .NET Framework 2.0 and Earlier
The .NET Framework 3.0 adds new technologies to the .NET Framework 2.0, which makes the .NET Framework 3.0 a superset of the .NET Framework 2.0. You can think of .NET Framework 3.0 as an "additive" release to the .NET Framework 2.0, as contrasted with a generational release where software is revised across the board. (For example, the .NET Framework 2.0 was a generational release over the .NET Framework 1.0.)

Because .NET Framework 3.0 is an additive release and uses the core run-time components from .NET Framework 2.0, it is completely backward compatible with the earlier version. Your existing .NET Framework 2.0 based-applications will continue to run without any modifications and you can safely continue your investments using the technologies that shipped with .NET Framework 2.0.

Installing the .NET Framework 3.0
The .NET Framework 3.0 is installed by default on Microsoft Windows Vista. On Microsoft Windows Server code-named "Longhorn", you can install the .NET Framework as a Windows Feature using Roles Management tools. On Windows XP and Windows Server 2003, installing .NET Framework 3.0 also adds any .NET Framework 2.0 components that are not already installed.
If .NET Framework 2.0 is already installed, the .NET Framework 3.0 installer adds only the files for Windows Presentation Foundation (WPF), Windows Workflow Foundation (WF), Windows Communication Foundation (WCF), and Windows CardSpace.

Components shared with .NET Framework 2.0 are installed in the following location:%windir%\Microsoft.NET\Framework\V2.0.50727
Components that are new to .NET Framework 3.0 are installed in the following location: %windir%\Microsoft.NET\Framework\V3.0
All components of the .NET Framework 3.0 reference assemblies are installed in the following location: %programfiles%\Reference Assemblies\Microsoft\Framework\v3.0

Uninstalling .NET Framework 3.0 will not remove the components shared with .NET Framework 2.0. To remove those components, you must first uninstall .NET Framework 3.0 and then separately uninstall .NET Framework 2.0.

Version Numbers for .NET Framework Assemblies
The .NET Framework 3.0 shares many components with .NET Framework 2.0, and the common language runtime (CLR) and base class libraries are the same as those in .NET Framework 2.0. Therefore, these shared components stay at version 2.0.

The version number 3.0 applies to all runtime and reference assemblies for Windows Communication Foundation (WCF), Windows Presentation Foundation (WPF), Windows Workflow Foundation (WF), and Windows CardSpace.

^ 基本上对我没有什么影响，因为我目前只关心Internet Application。所以，用好ASP.NET 2.0就是首要的。集中力量，先不去管.NET Framework 3.0的其他部分。