The entire control was wrapped within an Update Panel and dropped onto a Web Form.
When the postal code is entered by the user, the Update Panel detects the event (the corresponding Text Changed event in the back-end, either by specifying triggers or by using the Children As Triggers property set to true).
NET AJAX Extensions, including Web Services access and JSON serialization - Java Script Object Notation) and includes an Update Panel and Content Template within the main Web Forms page by default.This whitepaper is based on the Beta 2 release of the Visual Studio 2008 and the . NET AJAX Extensions into the Base Class Library (where it was previously an add-on component available for ASP. This whitepaper also assumes that you are using Visual Studio 2008 and not Visual Web Developer Express Edition; some project templates that are referenced may not be available to Visual Web Developer Express users. NET AJAX Extensions is the ability to do a partial or incremental page updates without doing a full postback to the server, with no code changes and minimal markup changes.The advantages are extensive - the state of your multimedia (such as Adobe Flash or Windows Media) is unchanged, bandwidth costs are reduced, and the client does not experience the flicker usually associated with a postback.It then checks to see whether an error was reported, and if so, processes the details of it, finally indicating to the runtime that the error was handled in custom script.The Script Manager control provides extensive support for localization of script strings and user interface components; however, that topic is outside of the scope of this whitepaper.Enabling partial rendering with this default page is as simple as revisiting Step 10 of this walkthrough and dropping controls onto the page.Markup-Enabled Properties: Quite simply, the above script registers a callback with the client-side AJAX runtime for when the asynchronous request has been completed.This means that the Update Panel can work with the default data-bound controls (such as the Grid View), with user controls, and they can be programmed in script.By default, when a partial page render is triggered, all Update Panel controls on the page will be refreshed, whether or not the Update Panel controls defined triggers for such action.To understand how the Update Panel works, so that you can best decide when its use is appropriate, you should examine the AJAX exchange.The following example uses an existing site and, Mozilla Firefox with the Firebug extension (Firebug captures XMLHttp Request data).