What is different is .net 3?

Essentials of Framework 1 and 2

NET Framework 3.0 is somewhat different from the 1.x and 2.0 .NET Framework. The first two .Net frameworks focused on allowing many different languages to communicate with a common set of libraries translated through the Common Language Runtime (CLR). Introduced with .NET 1.1 and enhanced with .NET 2.0, the CLR works on a relatively simple concept: A common runtime model executes code for any system running the .NET Framework. What this means to you as a developer is that you don’t need to keep relearning languages for different technologies. For instance, a C# developer who writes Windows Forms applications take the knowledge used for building forms and apply it to writing web pages. Similarly, a Visual Basic .NET developer can switch from writing mobile applications to writing web services. The CLR acts as an arbitrator and communicates back and forth.

.net Framework 3

The .NET 3.0 Framework is not improving upon existing technologies but rather introducing four new foundation technologies:

• Windows Presentation Foundation (WPF)
• Windows Communication Foundation (WCF)
• Windows Workflow Foundation (WWF)
• Windows CardSpace (WCS)

Each of these technologies is a new cornerstone that developers can leverage for new solutions.

Framework 3.5

.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. They include the following:

• Deep integration of Language Integrated Query (LINQ) and data awareness. This new feature will let you write code written in LINQ-enabled languages to filter, enumerate, and create projections of several types of SQL data, collections, XML, and DataSets by using the same syntax.
• ASP.NET AJAX lets you create 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 in Visual Studio 2008 for WF, WCF, and WPF, including the new workflow-enabled services technology.
• New classes in .NET Framework 3.5 base class library (BCL) that address many common customer requests.