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 »  Home  »  .NET Framework  »  A Brief Primer on Ajax
A Brief Primer on Ajax
by Roger McCook | Published  11/15/2006 | .NET Framework | Rating:
Roger McCook
Roger is an independent programmer in Atlanta, Georgia and president of McCook Software, Inc. (www.McCookSoftware.com). He focuses on Microsoft technologies including VB, C#, ASP.NET, and SQL Server. For the past eight years he has spent most of his time developing advanced systems for the telecom giant BellSouth (now a part of AT&T). Roger is a published author of many technical articles as well as fictional short stories. You can email him at: RogerMcCook@bellsouth.net 

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Ajax

AJAX is short for “Asynchronous JavaScript and XML.” 
 
AJAX is actually a name for a collection of technologies that have been around for a while: HML, JavaScript, XML, CSS, DOM, JSON, etc. 

In a nutshell, AJAX is about making web apps more flexible, interactive, responsive, and more like feature-rich windows programs. 

Historically, web apps are scoped at the page level. We are presented with a static page. We enter information, then click the submit button and wait while the entire page is sent to the server. Eventually a new page is displayed and we continue.   
  
There have been improvements at the browser level over the last ten years or so. First there were minor screen animations implemented with JavaScript. Then Microsoft introduced the Document Object Model (DOM), making JavaScript more effective in accessing and changing various objects on the web page. Dynamic HTML gave us even more power.

Now AJAX promises to make web pages more responsive, more interactive, by exchanging small amounts of data with the server behind the scenes instead of reloading entire web pages each time the user makes a change. Since the transfer is asynchronous, the user sees changes to the web page while they are still typing, without being interrupted. 

Ajax manipulates the current page within a user’s web browser using the document object model. It can be used for tasks such as updating or deleting records or returning search queries without having to fetch a full page each time a change is made. In these cases, only small requests and short responses are required, making the web apps seem smoother and more responsive.

The transfer is usually handled by the XMLHttpRequest object created by Microsoft but now implemented by a majority of browsers.

Microsoft’s implementation of Ajax is called ASP.NET AJAX. Microsoft integrates cross-browser client script libraries with the ASP.NET 2.0 development framework. Programmers are provided with a familiar development process and a programming model they already know from using server-side ASP.NET. The inclusion of controls and templates for drag-n-drop development and the tight integration with Visual Studio make it an attractive offering for developers. 

You are at a cocktail party and someone mentions Ajax. You stir your martini and say, “That’s about the asynchronous exchange of data between client and server in web applications using XML and JavaScript, right?”

They’ll be so impressed.

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