ASP.NET AJAX ARCHITECTURE

Microsoft ASP.NET AJAX enables you to quickly create Web pages that include a rich user experience with responsive and familiar user interface (UI) elements. ASP.NET AJAX provides client-script libraries that incorporate cross-browser ECMAScript (JavaScript) and dynamic HTML (DHTML) technologies, and it integrates them with the ASP.NET 2.0 server-based development platform. By using ASP.NET AJAX, you can improve the user experience and the efficiency of your Web applications.

ASP.NET AJAX Architecture

ASP.NET AJAX consists of client-script libraries and of server components that are integrated to provide a robust development framework. In addition to ASP.NET AJAX, you can use the ASP.NET AJAX Control Toolkit and the features in the ASP.NET AJAX Futures releases, which are both community supported.

AJAX Client-Server Architecture

The ASP.NET AJAX server components basically consists of ASP.NET web server controls and components to manage UI and and flow of an application, and to manage serialization, validation, control extensibility.

ASP.NET Web server controls:

1. ScriptManager : Manages script resources for client components, partial-page rendering, localization, globalization, and custom user scripts.
2. UpdatePanel : Enables you to refresh selected parts of the page, instead of refreshing the whole page by using a synchronous postback.
3. UpdateProgress : Provides status information about partial-page updates in UpdatePanel controls.
4. Timer : Performs postbacks at defined intervals. You can use the Timer control to post the whole page, or use it together with the UpdatePanel control to perform partial-page updates at a defined interval.

ASP.NET AJAX Web Services

ASP.NET AJAX provides Web services that you can use from client script to work with ASP.NET application services for forms authentication and user profiles.

ASP.NET AJAX Client Architecture

The ASP.NET AJAX client-script libraries be made of JavaScript (.js) files that provide features for object-oriented development. The object-oriented features included in the ASP.NET AJAX client-script libraries enable a high level of consistency and modularity in client scripting. The following layers are included in the ASP.NET AJAX script libraries:

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  A browser compatibility layer. This provides compatibility across the most frequently used browsers (including Microsoft Internet Explorer, Mozilla Firefox, and Apple Safari) for your ASP.NET AJAX scripts.
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  ASP.NET AJAX core services, which include extensions to JavaScript, such as classes, namespaces, event handling, inheritance, data types, and object serialization.
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  An ASP.NET AJAX base class library, which includes components such as string builders and extended error handling.
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  A networking layer that handles communication with Web-based services and applications, and that manages asynchronous remote method calls.
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  Support for JavaScript libraries that are either embedded in an assembly or are provided as standalone JavaScript (.js) files. Embedding JavaScript libraries in an assembly can make it easier to deploy applications and can solve versioning issues.
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  Support for accessing server-based forms authentication and profile information in client script. This support is also available to Web applications that are not created by using ASP.NET, as long as the application has access to the Microsoft AJAX Library.
  

ASP.NET AJAX Control Toolkit

The ASP.NET AJAX Control Toolkit is a collection of samples and components that show you some of the experiences you can create with rich client ASP.NET AJAX controls and extenders. The Control Toolkit provides samples and a powerful SDK to make it simple to create and reuse custom controls and extenders. You can download the ASP.NET AJAX Control Toolkit from the ASP.NET Ajax Web site. The ASP.NET AJAX Control Toolkit is community supported.

For more information:http://www.asp.net/AJAX/Documentation/Live/overview/default.aspx

Reference: asp.net site, wikipedia