What is it?

ASP.net Ajax is Microsoft's free framework for creating Ajax (Asynchronous Javascript and XML) web applications. At its simplest, it lets ASP developers do this - or add Ajax controls to their existing applications - without leaving their familiar drag-and-drop environment, and without having to understand Javascript or asynchronous communication with the host. According to the O'Reilly Network, it protects developers from "the underlying gibberish that makes it [Ajax] all work".

Ajax applications can have the kind of rich user interfaces normally associated with desktop applications. They are also more responsive, because instead of reloading the whole page when the user makes a change or a request, they exchange the minimum possible data with the server while the application remains available to the user.

While providing undoubted performance benefits, this violates a number of rules and safeguards -it "breaks" the back button which enables you to return to the unmodified page, and means the URL no longer identifies a single, unique state of a page.

ASP.net Ajax is supported by Visual Studio 2008, supplied as part of ASP.net 3.5, and can be downloaded for ASP.net 2.0.

Where did it originate?

ASP.net Ajax began with the codename Atlas. It was released as a separate download early in 2007, then included with .net Framework 3.5, released at the same time as Visual Studio 2008 at the end of last year.

What's it for?

ASP.net Ajax supports ASP.net-style server-side programming, client-side programming or a combination of both. Developers can add partial update functionality to existing applications by wrapping sections of their websites in the Ajax server control 'update panel', which enables the server controls to update without a post-back.

Those with a knowledge of Javascript can build client-side applications using the client-side Ajax framework, which is also shipped in a standalone version as the Microsoft Ajax Library. According to Microsoft's official ASP.net site, this framework can be used with other server-side technologies - such as PHP and ColdFusion - because it is not tightly coupled with ASP.net.

There are alternatives to Microsoft's Ajax offering for ASP.Net. Gaia Ajax Widgets for .net is a commercial library of Ajax modules, some of which are also available in open source form. Ajax.net Professional, a widely used, independently developed, free library for ASP.net which pre-dated Microsoft's support for Ajax, now appears to have been abandoned.

What makes it special?

ASP.net Ajax builds on generally available Microsoft skills - for example, Javascript debugging using Visual Studio 2008. Developers can also explore the possibilities of using other .net-supported languages as alternatives to Javascript.

How difficult is it to master?

Developers who want to move beyond using the supplied Ajax controls will have to get to grips with Javascript and D/X/HTML, and understand the XMLHttpRequest API.

What systems does it run on?

Microsoft says ASP.net Ajax supports all popular browsers (although not yet mobile devices). However, there may be compatibility issues because of different browsers' document object models, and the way they implement Javascript.

Rates of pay

ASP.net developers with Ajax £25,000 -£40,000.


For those who simply want to add Ajax controls to their ASP.net applications without going more deeply into Ajax development, the tutorials (and downloads) on Microsoft's site should be sufficient. See also ajaxwidgets.com and www.ajaxpro.info. Ajax will be covered in more depth in the next Hot Skills.

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This was first published in March 2008


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