ASP.NET is a framework for generating on-demand web pages, launched by Microsoft in July 2000, and used to implement web applications. This is a major evolution of Active Server Pages (ASP, aka Classic ASP), whereby this technique was incorporated into the Microsoft .NET platform.

Programming on ASP.NET is event-oriented, an event = something happened. In this programming style the system waits for something to happen, for example the user presses a button. A function is associated with this event, and this function will be executed automatically by the system when the user performs the action. In ASP.NET the web page and most widgets can cause events. Events also correspond to the start of the application or the connection of a user. Events may correspond to actions performed on the web browser, which can sometimes be treated with delay, because ASP.NET is executed by the web server

The ASP.NET engine is a filter plugged into the Internet Information Services (IIS) web server. It is distributed with the .NET framework. ASP.NET can be used with any programming language for the .NET platform (Visual Basic .NET, C #, JScript4 ...).