Object-oriented web application development supporting inheritance, polymorphism and other standard OOP features.
Based on Windows programming; the developer can make use of DLL class libraries and other features of the web server to build more robust applications that do more than simply rendering HTML.
ASP.NET 1.1
Mobile controls.
Automatic input validation.
ASP.NET 2.0
New data controls (GridView, FormView, DetailsView).
New technique for declarative data access (SqlDataSource, ObjectDataSource, XmlDataSource controls).
Navigation controls.
Master pages.
Login controls.
Themes.
Skins.
Web parts.
Personalization services.
Full pre-compilation.
New localization technique.
Support for 64-bit processors.
ASP.NET 3.0
Windows Presentation Foundation (WPF).
Windows Workflow Foundation (WF).
Windows Communication Foundation which can use ASP.NET to host services.
Windows CardSpace which uses ASP.NET for login roles.
ASP.NET 3.5
New data controls (ListView, DataPager).
ASP.NET AJAX included as part of the framework.
Support for HTTP pipelining and syndication feeds.
WCF Support for RSS, JSON, POX and Partial Trust.
LINQ.
ASP.NET 4.0
Parallel Extensions to improve support for parallel computing, which target multi-core or distributed systems.
New Visual Basic .NET and C# language features, such as statement lambdas, implicit line continuations, dynamic dispatch, named parameters, and optional parameters.
Support for Code Contracts.
Inclusion of new types to work with arbitrary-precision arithmetic (System.Numerics.BigInteger) and complex numbers (System.Numerics.Complex).