Original author(s)Microsoft
Initial releaseJanuary 23, 2007; 17 years ago (2007-01-23)
Operating systemMicrosoft Windows, Linux, macOS
TypeSoftware framework
LicenseMicrosoft Public License

ASP.NET AJAX, formerly called Atlas, is a set of extensions to ASP.NET[1] developed by Microsoft for implementing Ajax functionality. It is released under the Microsoft Public License (Ms-PL).[2]

Clients supporting Ajax

ASP.NET AJAX runs on the following browsers:


At present, the ASP.NET AJAX suite consists of the following components and packages:

Microsoft Ajax Library

The Microsoft Ajax Library is a JavaScript library that provides the features for the client portion of the ASP.NET AJAX framework.

Recently, new features have been announced as part of the ASP.NET AJAX 4.0 release:

The UpdatePanel Control

The UpdatePanel is an ASP.NET server control that updates portions of a web page without reloading it. Through a mechanism called asynchronous postback, the HTML for the region of the page wrapped by the control is sent by the server asynchronously through an Ajax request. The ASP.NET controls that have been specified as content in an UpdatePanel are able to cause either synchronous (traditional) or asynchronous postbacks, by means of triggers.

A trigger is an event coming from an ASP.NET control that causes an UpdatePanel to refresh its contents. Through triggers, an asynchronous postback can be started also by controls that are declared outside the region of the ASP.NET page wrapped by the UpdatePanel control.

In the following code, only the content of the Update control (the span element that displays the current date and time) is re-rendered every time the button is clicked.

<asp:Button ID="Button1" runat="server" Text="Refresh" />

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <asp:AsyncPostBackTrigger ControlID="Button1" EventName="Click" />
    <span><%= DateTime.Now %></span>

Web-services and JSON

ASP.NET AJAX framework brings JSONserialization features to the ASP.NET web-services and allows calling web-services from client-side JavaScript, even using third-party JavaScript-libraries like jQuery.

See also


Further reading