First, let's take a look at the ASP.NET AJAX framework architecture
(Figure 1):
Figure 1: The ASP.NET AJAX Framework architecture

Generally, as far as ASP.NET AJAX (called
'MS AJAX' later in this series) framework is concerned, we refer to the three
components as follows:
·
ASP.NET AJAX Essential Components, which corresponds
to the assemblies System.Web.Extensions.dll and System.Web.Extensions.Design.dll with three files: MicrosoftAjax.js, MicrosoftAjaxTimer.js,
and MicrosoftAjaxWebForms.js inside them.
·
ASP.NET AJAX Control Toolkit (with no
hint about it in Figure 1), which provides both ready-to-run samples and a
powerful SDK to simplify creating custom ASP.NET AJAX controls and extenders.
·
ASP.NET AJAX Futures January CTP (recently
replaced by a May
release, with the January one still available),
which corresponds to the assembly Microsoft.Web.Preview.dll
which contains three files: PreviewScript.js, PreviewGlitz.js, and PreviewDragDrop.js.
The ASP.NET 2.0 AJAX Futures January CTP provides additional
features and functionality that work alongside the ASP.NET AJAX Extensions.
Together, these releases enable development scenarios supported in the earlier
ASP.NET AJAX CTP releases in addition to newly added functionality.
To follow along with the samples in this series, you must
first have ASP.NET
2.0 AJAX Extensions 1.0 installed on your computer. Next, you can easily install
the ASP.NET 2.0 AJAX Futures January CTP by downloading ASPAJAXCTP.msi and running
it on your computer. Please carefully read the release notes which are
displayed following installation for more information on using the ASP.NET 2.0
AJAX Futures January CTP with your applications.
Author's Note: Recently, Microsoft has
just released another newer version named ASP.NET Futures May
2007 ("Futures") which contains an early developer preview of
features (especially the previous ASP.NET AJAX Futures January CTP—discussed here), as well as provides new features
including ASP.NET Silverlight server controls, new functionality for ASP.NET
AJAX Extensions, dynamic data controls, enhancements to dynamic languages, and
more.
Now, since our main interests lie in the ASP.NET AJAX
Futures January CTP, let's do further research into it.