The Microsoft .NET Framework 3.5 Beta 1 is a preview release of the latest version of the .NET Framework. Many ISV’s, enterprises and Microsoft product teams are successfully building on the new features Windows Workflow Foundation (WF), Windows Communication Foundation (WCF), Windows Presentation Foundation (WPF) and Windows CardSpace in the .NET Framework 3.0. Microsoft plans to continue to invest in the .NET Framework developer platform and in support of existing users the .NET Framework 3.5 has a minimal number of breaking changes. So that existing applications built for .NET Framework 2.0 or .NET Framework 3.0 should continue to run without requiring changes. The .NET Framework 3.5 adds new features in several major technology areas; including:

• Deep integration of Language Integrated Query (LINQ) and data awareness
  
• ASP.NET AJAX for quickly creating more efficient, more interactive and highly-personalized Web experiences that work across all the most popular browsers
  
• New web protocol support for building WCF services including AJAX, JSON, REST, POX, RSS, ATOM and several new WS-* standards
  
• Full tooling support for WF, WCF and WPF including the new workflow-enabled services technology
  
• New classes in the base class library (BCL) for the .NET Framework 3.5 address the most common customer requests.