In this walkthrough you will update part of a web page at a timed interval by using three ASP.NET AJAX server controls: the Script Manager control, the Update Panel control, and the Timer control.
If you try to work with one of these controls, and your website doesn't contain the required web.config file, errors appear in the This walkthrough introduced the basic concepts of using a Timer control and an Update Panel control to enable partial-page updates.You must add a Script Manager control to any page that contains an Update Panel control or Timer control.By default, a Timer control inside the panel will cause just the panel to refresh during an asynchronous postback.A Timer control outside a panel can cause the Update Panel to be refreshed if it is configured as a trigger for the panel.Traditionally webpages required reloading to update their content.
For web-based email this meant that users had to manually reload their inbox to check and see if they had new mail.
This had huge drawbacks: it was slow and it required user input.
When the user reloaded their inbox, the server had to reconstruct the entire web page and resend all of the HTML, CSS, Java Script, as well as the user's email. Ideally, the server should only have to send the user's new messages, not the entire page.
By 2003, all the major browsers solved this issue by adopting the XMLHttp Request (XHR) object, allowing browsers to communicate with the server without requiring a page reload.
The XMLHttp Request object is part of a technology called Ajax (Asynchronous Java Script and XML).
Using Ajax, data could then be passed between the browser and the server, using the XMLHttp Request API, without having to reload the web page.