Adam Calderon is a C# MVP and the Application Development Practice Lead at InterKnowlogy. He is an accomplished software developer, author, teacher, and speaker with more than 14 years of experience designing and developing solutions on the Microsoft platform. His involvement with ASP.NET AJAX began in late 2005 with his participation in the ASP.NET ATLAS First Access program and later as a member of the UI Server Frameworks Advisory Council. Adam was one of the fortunate few who were able to work on a production application that utilized ASP.NET AJAX in its alpha form and experienced firsthand the trials and tribulations of working in “beta land” on this exciting technology. Visit Adam's blog at http://blogs.interknowlogy.com/adamcalderon.

 

Joel Rumerman is a Senior .NET Developer at the CoStar Group, where he develops ASP.NET applications to support the company’s commercial real estate information business. He is an adept software developer with more than eight years of experience developing .NET applications and is active in the San Diego .NET community as an author and speaker. Joel has been working with ASP.NET AJAX since late 2005 when he started work on a large-scale application for a worldwide independent software vendor. This initial entry into the ASP.NET AJAX world provided him invaluable experience as he worked closely with Microsoft as a member of the ATLAS First Access program and participated in a Strategic Design Review of the technology. Joel has gone on to implement many more solutions using ASP.NET AJAX, including a Virtual Earth mash-up that maps commercial real estate properties. Visit Joel's blog at http://seejoelprogram.wordpress.com.

 

 

Preface Preface IntroductionServer controls are an integral aspect of every ASP.NET application we build. They encapsulate browser appearance and server functionality in a reusable object. They can be used across multiple pages within a single ASP.NET application as well as across multiple ASP.NET applications. ASP.NET comes with a lot of prebuilt server controls. We have simple controls such as the label and we have complex controls such as the GridView. We also have the ability to create our own server controls to meet a need not met by one of the existing controls by inheriting from the appropriate base class and overriding its methods as needed.This model of using server controls to encapsulate browser appearance and server functionality has served our needs well since the inception of ASP.NET 1.0, but our server control needs are changing.A new server control need that has recently surfaced is the ability to incorporate Ajax functionality directly into the server control.This need arose because our web applications need to be more responsive and visually interactive than the traditional ASP.NET repaint-the-entire-screen model and therefore the traditional server control supplies. This requirement has emerged because users are using web sites such as Gmail, Live.com, Yahoo! Mail, and others that don't repaint the screen every time they click a button or need to receive fresh data. Rather, they rely on Ajax to fetch fresh data and then update or add to a portion of the screen based upon that data. Because these web sites are heavily used and users really enjoy their experience while using these websites they expect other web sites to perform with the same elegance as they do. When a web site doesn't perform with the same elegance the user will often move onto another web site that does. Those popular applications have raised the bar for what is an acceptably user-friendly web site.Because our users are demanding a web site experience that essentially uses Ajax and we build our ASP.NET web sites using server controls, we need a way of easily creating server controls that not only encapsulate browser appearance and server functionality, but also include Ajax functionality so that the server control itself is Ajax-enabled.Taking a step back for a moment, unlike other technologies you might have read books on, ASP.NET AJAX server controls don't provide you with anything that you couldn't already do. We've always been able to embed Ajax-functionality into server controls ... it was just a real pain.There were a few different methods we could use to include the JavaScript with our server control such as embedding it as a resource, but we eventually ended up having to do the same three tasks. To make our server control have some serious client capabilities we always had to concatenate strings together to form JavaScript statements and functions, write browser sniffing statements to make sure that the JavaScript was cross-browser compatible, and add attributes or render out Html that attached the JavaScript functionality to the client versions of our server controls. It wasn't impossible, but it was error-prone and there was always this mingling of server code and JavaScript that was hard to maintain and even harder to read.Furthermore, if you had multiple server controls that had client capabilities it was difficult (but not impossible) to ensure that the client functions that each server control required didn't overwrite each other when rendered on the browser. Tracking down that problem was always a fun hour or so.The difficulty grew exponentially if we wanted to include a mechanism for asynchronously communicating with the server when the user pressed a button embedded in the server control. Even with a helper communication library there were always tri