.NET Framework 3.5 Architecture

.NET Framework 3.5 Architecture

.NET Framework Developer's Guide

Updated: July 2008

The .NET Framework version 3.5 builds upon versions 2.0 and 3.0 and their service packs. The .NET Framework version 3.5 Service Pack 1 updates version 3.5 assemblies and includes new service packs for versions 2.0 and 3.0. This topic briefly describes the relationship of the .NET Framework versions 2.0, 3.0, 3.5, and their service packs.

Relationship of the .NET Framework Versions 2.0, 3.0, and 3.5

The following are considered to be a part of the .NET Framework 3.5 SP1:

.NET Framework 2.0
.NET Framework 2.0 service packs 1 and 2, which update assemblies that are included in the .NET Framework 2.0.
.NET Framework 3.0, which uses the assemblies that exist in the .NET Framework 2.0 and its service packs, and includes the assemblies that are necessary for the technologies that are introduced in the .NET Framework 3.0. For example, PresentationFramework.dll and PresentationCore.dll, which are necessary for Windows Presentation Foundation (WPF), are installed with the .NET Framework 3.0.
.NET Framework 3.0 service packs 1 and 2, which update the assemblies that were introduced in the .NET Framework 3.0.
.NET Framework 3.5, which includes new assemblies that provide additional functionality to the .NET Framework 2.0 and 3.0.
.NET Framework 3.5 service pack 1, which updates assemblies that are included in the .NET Framework 3.5.

Each version of the .NET Framework can be installed independent of later versions, and each version will install earlier versions automatically if they are not already installed. Additionally, the .NET Framework 3.5 SP1 introduces the Client Profile setup package, which includes only assemblies used by client applications. For more information, see .NET Framework Client Profile.

Note:
Windows Vista does not support the standalone installation of the .NET Framework version 2.0 SP2 or version 3.0 SP2. Windows 2000 does not support the .NET Framework version 3.5 SP 1, nor the standalone installation of the .NET Framework version 3.0 SP 2.

An application uses the same assemblies regardless of whether it targets the .NET Framework version 2.0, 3.0, 3.5, or the Client Profile, and regardless of whether the assemblies have been updated on a user's computer. For example, an application that uses WPF and targets the .NET Framework 3.0 uses the same instance of the mscorlib assembly as an application that uses Windows Forms and targets the .NET Framework 2.0. If a user has installed a later framework version or service pack that has updated their copy of mscorlib.dll, then both applications will use the updated version of the assembly.

Note:
The relationship of the .NET Framework versions 2.0, 3.0, and 3.5 differs from the relationship of versions 1.0, 1.1, and 2.0. The .NET Framework versions 1.0, 1.1, and 2.0 are completely separate from each other, and one version can be present on a computer regardless of whether the other versions are present. When versions 1.0, 1.1, and 2.0 are on the same computer, each version has its own common language runtime, class libraries, compiler, and so forth. Application developers can choose which version to target. For more information, see Side-by-Side Execution, Targeting a Specific .NET Framework, and Targeting Specific .NET Frameworks with MSBuild.

Note:

The relationship of the .NET Framework versions 2.0, 3.0, and 3.5 differs from the relationship of versions 1.0, 1.1, and 2.0. The .NET Framework versions 1.0, 1.1, and 2.0 are completely separate from each other, and one version can be present on a computer regardless of whether the other versions are present. When versions 1.0, 1.1, and 2.0 are on the same computer, each version has its own common language runtime, class libraries, compiler, and so forth. Application developers can choose which version to target. For more information, see Side-by-Side Execution, Targeting a Specific .NET Framework, and Targeting Specific .NET Frameworks with MSBuild.

What Is Included in the .NET Framework 3.5 SP1

This section summarizes the technologies that are included in the .NET Framework version 3.5 SP1 and each framework version that it contains. This list is not exhaustive; it lists just some of the major technologies that ship in the .NET Framework.

.NET Framework 2.0

The following technologies shipped with the .NET Framework 2.0.

Common language runtime (CLR) and base class libraries.
Support for generic types and methods.
Compilers for C#, Visual Basic, C++, and J#.
ADO.NET.
ASP.NET.
Windows Forms.
Web services.

For a complete list of features new to the .NET Framework 2.0, see What's New in the .NET Framework Version 2.0.

.NET Framework 2.0 SP 1 and SP 2

The .NET Framework 2.0 service pack 1 and service pack 2 update the CLR and several assemblies that shipped with the .NET Framework 2.0 and can be installed independent of the .NET Framework 3.5 SP1. Most of the updates to .NET Framework 2.0 are nonbreaking changes, but there are a few cases where new API elements are added or behavior has changed. If your application relies on changes that shipped with .NET Framework 2.0 SP 1 or SP 2, then you can have your application target the .NET Framework 2.0 and ask your customers to download the .NET Framework 2.0 SP 1 or SP 2. However, if your application relies on new or changed functionality, it is recommended that your application target the .NET Framework 3.5 or the .NET Framework Client Profile.

.NET Framework 3.0

The .NET Framework 3.0 requires the .NET Framework 2.0 to be installed on the computer. If a user installs the .NET Framework 3.0 on a computer that does not have the .NET Framework 2.0, the .NET Framework 2.0 is installed automatically.

The following technologies are introduced with the .NET Framework 3.0:

Windows Presentation Foundation (WPF).
Windows Communications Foundation (WCF).
Windows Workflow Foundation (WF).

For more information, see What's New in the .NET Framework Version 3.0.

.NET Framework 3.0 SP 1 and SP 2

The .NET Framework 3.0 service pack 1 and service pack 2 update several assemblies that shipped with the .NET Framework 3.0 and can be installed independent of the .NET Framework 3.5. The updates include nonbreaking changes, new API elements, and additional functionality to the technologies that shipped with .NET Framework 3.0. If your application relies on changes that shipped with .NET Framework 3.0 SP 1 or SP 2, then you can have your application target .NET Framework 3.0 and ask your customers to download the .NET Framework 3.0 SP 1 or SP 2. However, if your application relies on new or changed functionality, it is recommended that your application target the .NET Framework 3.5 or the .NET Framework Client Profile.

.NET Framework 3.5

The .NET Framework 3.5 introduces new features for the technologies in 2.0 and 3.0 and additional technologies in the form of new assemblies. The following technologies are introduced with the .NET Framework 3.5:

Language Integrated Query (LINQ).
New compilers for C#, Visual Basic, and C++.
ASP.NET AJAX.

For a complete list of features new to the .NET Framework 3.5, see What's New in the .NET Framework Version 3.5.

.NET Framework 3.5 SP1

The .NET Framework 3.5 service pack 1 updates several assemblies that shipped with .NET Framework 3.5. The updates include nonbreaking changes, new API elements, and additional functionality to the technologies that shipped with .NET Framework 3.5. The following technologies are included with the .NET Framework 3.5 SP1: