Microsoft .NET Framework 3.5 contains many new features building incrementally upon .NET Framework 2.0 and 3.0, and includes .NET Framework 2.0 service pack 1 and .NET Framework 3.0 service pack 1.
 
.NET Framework 3.5 builds incrementally on the new features added in .NET Framework 3.0. For example, feature sets in Windows Workflow Foundation (WF), Windows Communication Foundation (WCF), Windows Presentation Foundation (WPF) and Windows CardSpace. In addition, .NET Framework 3.5 contains a number of new features in several technology areas which have been added as new assemblies to avoid breaking changes.

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