ASP.NET AJAX 4 adds to client-side data scenarios for both page and component developers. JSON data from the server can be rendered as HTML UI on the client in a highly manageable and efficient way, using ASP.NET AJAX templates.

A new DataContext component provides full change tracking and identity management on the JavaScript objects and arrays. Changes to the data resulting from user interaction with the client-rendered UI can be tracked in the DataContext, and uploaded to the server at any time, through a simple call to the SaveChanges method. Change sets are uploaded in a single batch request to the JSON service.

A key aspect is support for ADO.NET Data Services.

You can try out. The bits, reference, samples, and source code are available on CodePlex at ASP.NET AJAX 4 Preview 4.

Also included on the site are previews to the updates to ADO.NET Dynamic Data 4.0, WCF REST Starter Kit Preview 2, Lightweight Test Automation Framework Update.