IS Department


Developing Rich Web Apps With ASP.NET AJAX

Posted in Programming by Brian Russell on November 9, 2006

Developing Rich Web Applications with ASP.NET AJAX by Mir Tariq and another person.

First of all, this talked sucked.  I took notes, but they mostly covered a lot of the same things that Scott Guthrie did in the keynote.  That made most of this session a waste of time.

The UpdatePanel allows partial re-rendering of a page.  It works by doing the following actions:

  1. Intercepts the postback.
  2. Replaces the postback with a XMLHTTPRequest (normal AJAX style of talking with the server).
  3. Raises the postback on the server.
  4. The postback on the server runs through the pre-render phase.
  5. The server does a special render of only the controls in the update panel and spits that out to the requester (the update panel).
  6. The Document Object Model (DOM) on the web page is updated with the new content where appropriate (inside the UpdatePanel).

The UpdatePanel updates when controls inside the panel issue a postback, or other controls on the page outside of the UpdatePanel are marked as triggers for the UpdatePanel to update.

By default, all UpdatePanels on a page update at the same time.  If you want to only update one panel, you need to set the UpdateMode to conditional in order to use triggers.

You can call the UpdatePanel.Update method to force a refresh of the panel.  So when one panel is being updated, it may have done something on the backend that requires another panel to need refreshed.  At this point in your code behind, you just call the Update method of that panel to get it refreshed as well as the panel that was originally being updated.

Here is a term I have known for awhile, but thought I would present to you.  JSON (JavaScript Object Notation) is the standard way to transfer objects in JavaScript.  This isn’t a MS standard, it is a industry standard.  MS uses it to transfer objects with its AJAX library.

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