Interesting article on CodeProject:
Introduction
One of the challenges that every ASP.NET 1.x web developer faced is that there isn't any native support for script callbacks to server without post-back of the current page. For example, retrieving and presenting the details of a selected employee in a dropdown list without forcing the full page refresh, and this is particularly an expensive call for UI-rich pages. So, how can we handle this?
Thanks to the ASP.NET team, they've built in this feature in ASP.NET 2.0, which allows calls to server events from client code without causing the page to post back and refresh. This is great, but we have to consider 2 facts: Time and Money. For time, we have to wait until ASP.NET 2.0 is released and we can't do anything in the meanwhile. For Money, we may be forced to upgrade Visual Studio .NET IDE from 2002/2003 to 2005 if we can't live without the Visual Studio.NET IDE. More importantly, implementing the script callbacks in ASP.NET 1.x isn't that hard at all. So, what are we waiting for?
Thanks to the extensible architecture of Page Controller framework, it gives developers the flexibility in hand to extend its functionalities, where native support is not sufficed. In this article, I'll walk you through the process of implementing the Script Callbacks Framework, and also provide a simplified but effective framework that you can use in ASP.NET 1.x.