ASP.NET is a web application framework introduced and marketed by Microsoft to allow programmers to build dynamic web sites, web applications and web services. First verson of ASP.NET (verson 1.0) was released in January 2002 as  successor  to microsoft Active Server Page technology.ASP.NET is built on the Common Language Runtime (CLR), which allows programmers to write ASP.NET code using several supported .NET language. The ASP.NETSOAP extension framework allows ASP.NET components to process SOAP messages.

Characteristics

Pages

.NET pages,well known as "web forms", are the main building block for application development.Web forms are contained in files with an ".aspx" extension.

Code-behind model

Microsoft recommends dealing with dynamic program code by using the code-behind model, which places this code in a separate file or in a specially designated script tag. Code-behind files typically have names like MyPage.aspx.cs or MyPage.aspx.vb while the page file is MyPage.aspx (same filename as the page file (ASPX), but with the final extension denoting the page language). This practice is automatic in Microsoft Visual Studio and other IDEs. When using this style of programming, the developer writes code to respond to different events, like the page being loaded, or a control being clicked, rather than a procedural walk through the document.

User controls

User controls are encapsulations of sections of pages which are registered and used as controls in ASP.NET.

Custom controls

Programmers can also build custom controls for ASP.NET applications. Unlike user controls, these controls don't have an ASCX markup file, having all their code compiled into a DLL file.

Rendering technique

ASP.NET uses a visited composites rendering technique. During compilation, the template (.aspx) file is compiled into initialization code which builds a control tree (the composite) representing the original template.

State management

ASP.NET applications are hosted by a web server and are accessed using the stateless HTTP protocol. As such, if an application uses stateful interaction, it has to implement state management on its own. ASP.NET provides various functions for state management