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.
Training
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.