Professional ASP.NET 3.5 AJAX

11.2. Building a Server-Side ASP.NET AJAX Control

Creating custom ASP.NET AJAX client-side controls is a fairly intensive exercise in JavaScript. Calling control methods, handling events, and even instantiating the control itself requires JavaScript code to be written. While some ASP.NET developers understand how to write JavaScript code, others may not have a complete understanding of the language and may prefer to work with server-side objects that can be manipulated using VB.NET or C#. They may prefer to be shielded from JavaScript code whenever possible.

Because server-side controls can output both HTML and JavaScript, they're good candidates for use with ASP.NET AJAX client-side controls. Developers familiar with defining and interacting with server-side controls can use an AJAX-enabled server-side control without having to worry about the client-side complexities. A nice "feature" of ASP.NET AJAX server-side controls is that once you have created the client-side script that handles all of the HTML output and event handling (as with the AlbumViewer control shown in this chapter), going a little further to create a server-side control is fairly straightforward and requires very little VB.NET or C# code. After all, most of the control's functionality is performed by the client-side script.

There are a few different paths to creating an ASP.NET AJAX server control. To choose the correct path, you need to decide what type of control you want to create. Will the control be visual, ...