The opinions mentioned herein are solely mine and do not reflect those of my employer

Wanted to post this for a long time but couldn’t.  I have been an ASP.NET Developer for quite sometime and have worked with version 1.1, 2.0, 3.5 as well as the latest 4.0.

With ASP.NET 2.0 and Visual Studio 2005, came the era of AJAX and rich UI style web applications.  So, ASP.NET AJAX (codenamed “ATLAS”) was released almost an year later.  This was called as ASP.NET 2.0 AJAX Extensions.  This release was supported further with Visual Studio 2005 Service Pack 1.

The initial release of ASP.NET AJAX had 3 components

ASP.NET AJAX Library – Client library that is used internally by the server controls as well as scripts that can be used to write hand coded ajax style pages

ASP.NET AJAX Extensions – Server controls i.e. ScriptManager,Proxy, UpdatePanel, UpdateProgress and Timer server controls.  Works pretty much like other server controls in terms of development and render client side behavior automatically

AJAX Control Toolkit – Set of server controls that extend a behavior or a capability.  Ex.- AutoCompleteExtender

The AJAX Control Toolkit was a separate download from CodePlex while the first two get installed when you install ASP.NET AJAX Extensions.

With Visual Studio 2008, ASP.NET AJAX made its way into the runtime.  So one doesn’t need to separately install the AJAX Extensions.  However, the AJAX Control Toolkit still remained as a community project that can be downloaded from CodePlex.  By then, the toolkit had close to 30 controls.

So, the approach was clear viz., client side programming using ASP.NET AJAX Library and server side model using built-in controls (UpdatePanel) and/or AJAX Control Toolkit.

However, with Visual Studio 2008 Service Pack 1, we also added support for the ever increasing popular jQuery library.  That is, you can use jQuery along with ASP.NET and would also get intellisense for jQuery in Visual Studio 2008.

Some of you who have played with Visual Studio 2010 Beta and .NET Framework 4 Beta, would also have explored the new AJAX Library which had a lot of templates, live bindings etc., 

But, overall, the road map ahead makes it much simplified.

For client side programming using JavaScript for implementing AJAX in ASP.NET, the recommendation is to use jQuery which will be shipped along with Visual Studio and provides intellisense as well.

For server side programming one you can use the server controls like UpdatePanel etc., and also the AJAX Control Toolkit which has close to 40 controls now.  The AJAX Control Toolkit still remains as a separate download at CodePlex.  You can download the different versions for different versions of ASP.NET at

The Microsoft AJAX Library will still be available through the CDN (Content Delivery Network) channels.  You can view the CDN resources at  The versions available in CDN include the 3.5 version as well as 4.0 version of the scripts.  This is specifically to help if you already invested in development using ASP.NET AJAX 4.0 as well as for those who don’t want to use jQuery

Similarly even jQuery and the toolkit would be available as CDN resources in case you chose not to download and have them as a part of your application.

I think this makes AJAX development pretty simple.  Earlier, having Microsoft AJAX Library as well as jQuery for client side scripting was kind of confusing on which one to use.  With this roadmap, it makes it simple and clear.

You can read more on this at

I hope this post provided some clarity on the AJAX roadmap as I could decipher from various product teams.