Ajax (programming)

BLOG.WALEEDMOHAMED.NET Ajax (programming) ASP.NET AJAX Overview Eng.Waleed M. 2007 ARENY.NET

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Introduction Ajax, shorthand for "Asynchronous JavaScript and XML," is a web development technique for creating interactive web applications. The intent is to make web pages feel more responsive by exchanging small amounts of data with the server behind the scenes, so that the entire web page does not have to be reloaded each time the user requests a change. This is intended to increase the web page's interactivity, speed, and usability. JavaScript + Xml Ajax Increase the web page's Interactivity Speed Usability The Ajax technique uses a combination of:  XHTML (or HTML) and CSS, for marking up and styling information.  The DOM accessed with a client-side scripting language, especially ECMAScript implementations such as JavaScript and JScript, to dynamically display and interact with the information presented.  The XMLHttpRequest object is used to exchange data asynchronously with the web server. In some Ajax frameworks and in certain situations, an IFrame object is used instead of the XMLHttpRequest object to exchange data with the web server, and in other implementations, dynamically added <script> tags may be used.  XML is sometimes used as the format for transferring data between the server and client, although any format will work, including preformatted HTML, plain text, JSON and even EBML. These files may be created dynamically by some form of server-side scripting. BLOG.WALEEDMOHAMED.NET Page 3 .net

Like DHTML, LAMP and SPA, Ajax is not a technology in itself, but a term that refers to the use of a group of technologies. Ajax • XHTML (or HTML) and CSS Styling • client-side scripting language Interact • XMLHttpRequest object Data Exchange • XML Data Formatting Ajax Advantages: 1- User interface Helping make the Web even more interactive and popular than it currently is, The page often can be updated dynamically, allowing a faster response to the user's interaction. 2- Bandwidth usage "load on demand" By generating the HTML locally within the browser, and only bringing down JavaScript calls and the actual data, Ajax web pages can appear to load relatively quickly since the payload coming down is much smaller in size. An example a table structure with related TD and TR tags can be produced locally in the browser and not brought down with the first page of the document. In addition to "load on demand" of contents, some web based applications load stubs of event handlers and then load the functions on the fly. 3- Separation of data, format, style, and function A less specific benefit of the Ajax approach is that it tends to encourage programmers to clearly separate the methods and formats used for the different aspects of information delivery via the web. BLOG.WALEEDMOHAMED.NET Page 4 .net

Disadvantages 1- Browser integration The dynamically created page does not register itself with the browser history engine, so triggering the "Back" function of the users' browser might not bring the desired result. Solution: using invisible IFRAMEs to invoke changes that populate the history used by a browser's back button. Google Maps, for example, performs searches in an invisible IFRAME and then pulls results back into an element on the visible web page Another issue is that dynamic web page updates make it difficult for a user to bookmark a particular state of the application. Solution: many of which use the URL fragment identifier to keep track of, and allow users to return to, the application in a given state. This is possible because many browsers allow JavaScript to update the fragment identifier of the URL dynamically, so that Ajax applications can maintain it as the user changes the application's state. This solution also improves back-button support. It is, however, not a complete solution. 2- Response-time concerns" Network latency" Network latency — or the interval between user request and server response — needs to be considered carefully during Ajax development. 3- Search engine optimization" hidden web " Search engines do not generally execute the JavaScript code required for Ajax functionality. This problem is not specific to Ajax, as the same issue occurs with sites that provide dynamic data as a full-page refresh in response to, say, a form submit (the general problem is sometimes called the hidden web). 4- Reliance on JavaScript Ajax relies on JavaScript, which may be implemented differently by different browsers or versions of a particular browser, Implementing Mutual Exclusion in JavaScript may solve the problem. BLOG.WALEEDMOHAMED.NET Page 5 .net

5- Accessibility Non-Ajax users would ideally continue to load and manipulate the whole page as a fallback, allowing the developers to preserve the experience of users in non-Ajax environments (including all relevant accessibility concerns) while giving those with capable browsers a much more responsive experience. 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. Server Script Manager -Localization Update Panel -Globalization Update Progress -Debugging Timer Server Control Script Support -Tracing Asp.net Ajax Extensions Authentication & -Proxy Generation Application Services Web Services -Page Methods Profile -Xml & JSON Serialization Client Asynchronous Non visual Results , Xml & JSON Components , Serialization , web & Behavior , Controls App Services Networking Components Ms Ajax library Java script base class Support 4 Ms IE , Extensions , type Core Services Browser Compatibility Mozilla Firefox , systems , event , apple safari serialization ASP.NET AJAX Server Architecture The ASP.NET AJAX server components consist of ASP.NET Web server 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. BLOG.WALEEDMOHAMED.NET Page 6 .net

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. 1- Script Manager Manages script resources for client components, partial-page rendering, localization, globalization, and custom user scripts. The Script Manager control is required in order to use the Update Panel, Update Progress, and Timer controls. 2- Update Panel Enables you to refresh selected parts of the page, instead of refreshing the whole page by using a synchronous postback. 3- Update Progress Provides status information about partial-page updates in Update Panel 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. This enables you to use client script to help protect resources by using forms authentication and to persist user-specific settings on the server. 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. ASP.NET AJAX Server Control Extensibility ASP.NET AJAX enables you to create custom ASP.NET AJAX server controls that include client behaviors. For more information, see the tutorials in ASP.NET AJAX Extensibility and the Microsoft ASP.NET AJAX Control Toolkit. BLOG.WALEEDMOHAMED.NET Page 7 .net

ASP.NET AJAX Client Architecture The ASP.NET AJAX client-script libraries consist 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:  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.  ASP.NET AJAX core services, which include extensions to JavaScript, such as classes, namespaces, event handling, inheritance, data types, and object serialization.  An ASP.NET AJAX base class library, which includes components such as string builders and extended error handling.  A networking layer that handles communication with Web-based services and applications, and that manages asynchronous remote method calls.  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.  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.  Support for release and debug modes and localization support for both assembly-embedded and standalone JavaScript files. Debugging The ASP.NET AJAX architecture provides a model for release and debug modes. Release mode provides error checking and exception handling optimized for performance, with minimized script size. Debug mode provides more robust debugging features, such as type and argument checking. If you create debug versions of custom client scripts or script resources, ASP.NET runs the debug versions when the application is in debug mode. This enables you to throw exceptions in debug scripts while minimizing the size of release code. A debug helper class, Sys.Debug, provides methods for displaying objects in readable form at the end of a Web page. It also shows trace messages, enables you to use BLOG.WALEEDMOHAMED.NET Page 8 .net

assertions, and lets you break into the debugger. An extended Error Object object API provides helpful exception details with support for release and debug modes. Localization and Globalization The ASP.NET AJAX server and client architecture provides a model for localizing and globalizing client script. This enables you to design applications that use a single code base to provide UI for many locales (languages and cultures). For example, ASP.NET AJAX enables JavaScript code to format Date or Number objects automatically according to culture settings of the user's browser, without requiring a postback to the server ASP.NET AJAX builds on the foundation of the ASP.NET 2.0 localization model. It provides additional support for localized script files that are embedded in an assembly or that are provided as .js files on disk. ASP.NET AJAX can serve localized client scripts and resources automatically for specific languages and regions. 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. 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 that is not included in the Microsoft ASP.NET AJAX release. This includes additional extender controls, support for client declarative syntax (xml- script), and more. To download and learn more about the Futures release, see the ASP.NET AJAX Web site. BLOG.WALEEDMOHAMED.NET Page 9 .net

Ajax (programming)

by Flair Systems on May 16, 2010

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Ajax (programming) — Document Transcript