What Is ASP.NET AJAX?

ASP.NET AJAX is the name of Microsoft’s AJAX solution, and it refers to a set of client and server technologies that focus on improving web development with Visual Studio. Other companies have their own AJAX solution, often taking a radically different approach, but Microsoft has sought to build upon the popular ASP.NET technology by developing a comprehensive set of script libraries as well as server programming enhancements. One piece, the Microsoft AJAX Library, is a JavaScript library that works on a variety of browsers and serves to simplify JavaScript development. It provides you with the capability to easily write JavaScript using an object-oriented programming approach similar to code-behind programming in ASP.NET. You can use the functions of the Microsoft AJAX library to interact with the DOM, dynamically update portions of the page, communicate with the web server asynchronously, and write rich animations on the page. You’ll learn about the client features in Chapters 6 and 7, but for now think of the Microsoft AJAX Library as a type system and set of class libraries that simplify writing JavaScript to enhance the user experience, manipulate the DOM, and communicate with the web server. The huge benefit in using this library is that it abstracts the tedious low-level DHTML programming into an OOP model that is much easier to work with.

The other part of the ASP.NET AJAX release is the server-side ASP.NET 2.0 AJAX Extensions. These extensions build on top of the ASP.NET classes and controls and leverage the Microsoft AJAX Library sent to the browser. They make it easy to quickly take advantage of AJAX technologies to enrich an application. Through a set of standard web services, ASP.NET AJAX is also able to leverage server-based application services such as authentication and user profile storage. The extensions both extend some of the existing ASP.NET controls by adding new behaviors and include a new set of server controls that make it easy to do asynchronous updates to a page and leverage server resources.

The client and server pieces of ASP.NET are shown in Figure 1-3. ASP.NET is built on top of the Microsoft Internet Information Services (IIS) web server. ASP.NET AJAX builds on top of that and the web services it includes. The Microsoft AJAX Library runs in the browser to manipulate the DOM, communicate asynchronously with the web server, and take advantage of ASP.NET services.