ASP.NET is a server-side Web application framework designed for Web development to produce dynamic Web pages.It was developed by Microsoft to allow programmers to build dynamic web sites, web applications and web services.It was first released in January 2002 with version 1.0 of the .NET Framework, and is the successor to Microsoft's Active Server Pages (ASP) technology. ASP.NET is built on the Common Language Runtime (CLR), allowing programmers to write ASP.NET code using any supported .NET language. The ASP.NET SOAP (Simple Object Access Protocol) extension framework allows ASP.NET components to process SOAP messages.

ASP.NET Web pages, known officially as Web Forms, are the main building blocks for application development.Web forms are contained in files with a ".aspx" extension; these files typically contain static (X)HTML markup, as well as markup defining server-side Web Controls and User Controls where the developers place all the rc content for the Web page.Additionally, dynamic code which runs on the server can be placed in a page within a block <% -- dynamic code -- %>,which is similar to other Web development technologies such as PHP, JSP, and ASP. With ASP.NET Framework 2.0,Microsoft introduced a new code-behind model which allows static text to remain on the .aspx page, while dynamic code remains in an .aspx.vb or .aspx.cs or .aspx.fs file (depending on the programming language used).