AJAX DropDownList

Just recently, I published a new article in CodeProject about implementation of AJAX (Asynchronous Javascript and XML) in a dropdownlist.

AJAX DropDownList is a custom control, inherited from System.Web.UI.WebControls.DropDownList. What differs this control from the normal DropDownList is the ability to fetch data asynchronously in the background without requiring any postbacks. Thus, an AJAX DropDownList can be dynamically populated from the client side using Javascript. Moreover, AJAX DropDownList implements Observer pattern to 'listen' to the change event of another AJAX DropDownList, and to 'broadcast' its change event to the other AJAX DropDownLists. This feature allows us to create a group of dependent dropdownlists, where a change in the first dropdownlist will trigger change on the second dropdownlist, and subsequently trigger change on the third dropdownlist, and so on...

Please read the article in Code Project for more details.