ASP.NET (originally called ASP+) is the next generation of Microsoft's active server pages, a feature of the Internet Information Server. Both ASP and ASP.NET allow a Web site programmer to dynamically build Web pages on the fly by inserting queries to a relational database within the Web page.

ASP.NET is different than its predecessor in two major ways: it supports code written in compiled languages such as Visual Basic, C++, C#, and Perl; and it features server controls that can separate the code from the content, allowing live, on-screen editing of pages.

Microsoft offers a client-based tool entitled Visual Studio .NET, which allows programmers to visually design ASP.NET Web forms using drag and drop controls, and enjoy full-fledged code support including statement completion and color-coding. VS.NET also provides integrated support for debugging and deploying ASP.NET Web applications.

Enterprise versions of VS.NET deliver life-cycle features to help organizations plan, analyze, design, build, test, and coordinate teams that develop ASP.NET Web applications. These include UML class modeling, database modeling (conceptual, logical, and physical models), testing tools (functional, performance and scalability), and enterprise frameworks and templates, all available within the integrated Visual Studio .NET environment.

Although ASP.NET is not backward compatible with ASP, it is able to run side by side with ASP applications. ASP.NET files can be recognized by their .aspx extensions. The ASP.NET feature runs on IIS side by side with classic ASP on Windows 2000, Windows XP and Windows 2003 Server operating systems platforms. In this way, existing ASP applications continue to be processed by ASP dynamic link libraries while new ASP.NET pages are processed by the ASP.NET engine. Users can migrate application by application, or single pages. ASP.NET even lets consumers continue to use existing classic COM business components.

ASP.NET is also a powerful tool because it allows Web site builders to adopt new application models that can extend an application's reach to new customers and partners. ASP.NET supports XML Web services, which allow applications to communicate and share data over the Internet, regardless of operating system or programming language.

ASP.NET makes exposing and calling XML Web services simple. Any class can be converted into an XML Web service with just a few lines of code, and can be called by any SOAP client. Likewise, ASP.NET makes it easy to call XML Web services from an application. No actual knowledge of networking, XML, or SOAP is required.

Freely available for download and installation, ASP is a powerful tool, providing an advanced framework designed for use by professional Web designers, programmers and database specialists. Free online tutorials offer a series of ASP.NET samples and supporting commentary designed to quickly acquaint end-users with the syntax, architecture, and power of the ASP.NET Web programming framework.

Due to the power functionality of ASP.NET programming, hosting for the framework has become a common feature among Windows-based service providers. ASP.NET programs can be composed in a text editor or in VS.NET and uploaded to a hosting account with an ASP.NET engine installed.

The code is then processed through that engine and in turn can access database applications such as Microsoft SQL server. The challenge consumers face is finding a host that has effectively and efficiently deployed ASP.NET services.

ASP.NET is demanding with respect to memory use and execution time, which is due in large part to its longer code path. For Web-based applications, these limitations can be a serious problem, because on the Web, an application is likely to scale to thousands and thousands of users per second.

Customers will want to find a Web host that can guarantee top-notch performance and security on the Windows platform. Users might also want to consider using a streamlined UNIX-based Apache Web server system that supports ASP.NET.