ASP.NET AJAX Overview

Introduction

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. Using ASP.NET AJAX, you can improve both the user experience and the efficiency of your Web applications.

Why Use ASP.NET AJAX?

ASP.NET AJAX enables you to build rich Web applications that have many advantages over Web applications that are completely server-based. ASP.NET AJAX applications offer:

• Improved efficiency by performing significant parts of a Web page's processing in the browser.
• Familiar UI elements such as progress indicators, tooltips, and pop-up windows.
• Partial-page updates that refresh only the parts of the Web page that have been updated.
• Client integration with ASP.NET application services for forms authentication and user profiles.
• Integration of data from different sources through calls to Web services.
• A framework that simplifies customization of server controls to include client capabilities.
• Support for the most popular and commonly used browsers, including Microsoft Internet Explorer, Mozilla Firefox, and Apple Safari.

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 community-supported features in the ASP.NET AJAX Futures releases.

ASP.NET AJAX Server Components

The ASP.NET AJAX server components consist of ASP.NET controls and components to manage the UI and flow of an application, and to manage serialization, validation, control extensibility, and so on. There are also ASP.NET Web services that enable you to access ASP.NET application services for forms authentication and user profiles.

ASP.NET AJAX Server Controls

The ASP.NET AJAX server controls consist of server and client code that integrate to produce AJAX-like behavior. The following list describes the most frequently used ASP.NET AJAX server controls.

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

ASP.NET AJAX Web Services

ASP.NET AJAX exposes ASP.NET application services for forms authentication and user profiles to client script by using Web services. This enables you to help protect resources by using forms authentication and to persist user-specific settings on the server by using client script. In addition, ASP.NET AJAX includes network components that make it easy to return results from any Web service call.
For information and examples, see Asynchronous Communication Layer Overview and ASP.NET Application Services Tutorials.

ASP.NET AJAX Server Control Extensibility

ASP.NET AJAX enables you to create custom ASP.NET AJAX server controls that include client behaviors. For information and examples, see the ASP.NET AJAX Extensibility tutorials and the Microsoft ASP.NET AJAX Control Toolkit.

ASP.NET AJAX Client Components

The ASP.NET AJAX client-script libraries consist of JavaScript (.js) files that provide features for object-oriented development. This has not been previously available to JavaScript developers. The object-oriented features included in the ASP.NET AJAX client-script libraries enable a new level of consistency and modularity in client scripting. The following layers are included in the ASP.NET AJAX script libraries:

1. 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.
2. ASP.NET AJAX core services,
   which include extensions to JavaScript, such as classes, namespaces, event handling, inheritance, data types, and object serialization.
3. An ASP.NET AJAX base class library,
   which includes components such as string builders and extended error handling.
4. A networking layer
   that handles communication with Web-based services and applications, and that manages asynchronous remote method calls.

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 both samples and a powerful SDK to simplify creating and reusing your custom controls and extenders.

ASP.NET AJAX Community-supported Futures Releases

The ASP.NET AJAX community-supported Futures releases provide features that extend the core ASP.NET AJAX platform with functionality that remains under development and is not included in the Microsoft ASP.NET AJAX release. This includes additional extender controls, support for client declarative syntax (xml-script), and more.