The .NET Framework is an integral Windows component that supports building and running the next generation of applications and Web services. The key components of the .NET Framework are the common language runtime (CLR) and the .NET Framework class library, which includes ADO.NET, ASP.NET, Windows Forms, and Windows Presentation Foundation (WPF). It provides a managed execution environment, simplified development and deployment, and integration with a wide variety of programming languages.
The documentation for the .NET Framework includes an extensive class library reference, conceptual overviews, step-by-step procedures, and information about samples, compilers, and command-line tools. To locate the information that interests you, see the following list of main topic areas.
.NET Framework 4 beta was made available with experimental software transactional memory support.Whether this functionality will be available in the final version of the framework has not been confirmed.
In conjunction with .NET Framework 4, Microsoft will offer a set of enhancements, codenamed Dublin, for Windows Server 2008 application server capabilities. Dublin will extend IIS to be a “standard host” for applications that use either WCF or WF.
There are lot of new features in ASP.NET 4.0 like html, jscript snippets, new development profiles, generate form usage, enablePersistedSelection, web.config transformation, compression enabling for session values etc.