How to make a Gmail-like loading indicator with ASP.NET Ajax

The application uses a few ASP.NET Ajax controls so I was pretty surprised when the customer sent me an email saying that he liked all the dynamic loading and the fact that he could reorder "things" using drag&drop and saving them without waiting the page to reload, but it took him a while to understand was going on. The first time he clicked the button, and since nothing happened, he thought that something was going wrong, so he kept clicking on the button, an yet nothing happening.

The problem was that since all the Ajax interactions happen behind the scenes asynchronously, the user doesn't understand what's going on: sometimes the user doesn't need to know what's going on (like when you are just reloading some data), but when he presses a button he needs to know that he did the right thing and that something is happening. With the "old style" ASP.NET a postback would have been initiated, so it was obvious that something was happening, but how to do it using Ajax?

That is pretty easy to accomplish with ASP.NET: just drop in an UpdateProgress control and it will be displayed when an Ajax postback happens.

But, as default behavior, the UpdateProgress is displayed in the position where it is added to the page, so, if your page is longer than a scroll page, the indicator could not be visible: it has to be positioned relative to the browser window and not relative the html document.

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New Features in ASP.NET 3.5

ASP.NET has for long been a popular web application development platform. ASP.NET 2.0 added a lot of new features compared to its earlier counterpart, i.e., ASP.NET 1.1. With ASP.NET 3.5, you have even more features. This article will present the new features that have been added to ASP.NET and Visual Studio 2008.


In ASP.NET 3.5, a new tool has been introduced called the ASP.NET Merge Tool. You can use this tool for merging pre-compiled assemblies. No, this is not all. There isa lot of other exciting features and we will explore each of them as we progress through this article.

The most significant improvements in ASP.NET are:

* Integrated Ajax Support
* New Data Controls (ListView and DataPager)
* The LinqDataSource Control

Visual Studio 2008 has also included some features for an improved web application development experience. Here is the list of such improvements:


* Support for LINQ
* IntelliSense for JavaScript and ASP.NET Ajax
* Improved Design time experience

We will explore each of these features as we progress through this article.

New ASP.NET Features

We will start our discussion with the improvements in ASP.NET. The sections that follow discuss the significant improvements made in ASP.NET 3.5.

Integrated Ajax Support

Before we proceed further, let us have a quick look at what Ajax is all about. Ajax, an acronym for Asynchronous JavaScript and XML, is a cross-platform technology that can be used to make your web pages fast, rich and responsive. Note that in Ajax enabled web applications, requests are sent to the server only for the data that is needed. Incidentally, Ajax is mainly a mix of Javascript, Html, CSS, XML, DOM and the XMLHttpRequest Object. It is a technology that can be used to send and receive data (usually in XML format) from a server-side application using Javascript. According to Enrich Peterson, "AJAX-enabled pages provide a slick, responsive user experience, making web-based applications function more like desktop-based ones".

MSDN states, "ASP.NET AJAX is a set of technologies to add AJAX (Asynchronous JavaScript and XML) support to ASP.NET. It consists of a client-side script framework, server controls, and more. Although AJAX is essentially a client-side technique, most of its real-world deployments call for server-side processing."

Here is a list of the advantages of using Ajax in web applications.

* Reduction of unnecessary web server hits, i.e., the round trips are minimized
* Rich, responsive user interface
* Real-time web page updates
* Language neutrality
* Faster web page renderings
* Less consumption of server’s resources (memory and processor load is reduced)

Ajax was introduced in ASP.NET as a separate add-on called ASP.NET 2.0 AJAX Extensions. This extensions library enabled you to design and implement Ajax enabled web applications using ASP.NET. The ASP.NET 2.0 framework incorporates the client script libraries of the ASP.NET Ajax framework. "The framework includes two distinct yet not mutually exclusive API's: client and server, which enable the developers to accomplish AJAX functionalities using direct client-side programming, traditional server-side programming, or any combination of both".

And, you also have the ASP.NET AJAX Control Toolkit, a community project from Microsoft that comprises of a SDK and code samples. According to Microsoft, "The ASP.NET AJAX Control Toolkit provides a set of sample controls and extenders that makes it a snap to spice up your web site with rich functionality".

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Advanced ASP.NET AJAX Server Controls For .NET Framework 3.5

ASP.NET AJAX server controls can encapsulate even the most powerful AJAX functionality, helping you build more elegant, maintainable, and scalable applications. This is the first comprehensive, code-rich guide to custom ASP.NET AJAX server controls for experienced ASP.NET developers. Unlike other books on ASP.NET AJAX, this book focuses solely on server control development and reflects the significant improvements in ASP.NET 3.5 AJAX and the latest Visual Studio 2008 features for streamlining AJAX development

Adam Calderon and Joel Rumerman first review the core Microsoft AJAX Library and JavaScript techniques needed to support a rich client-side experience. Next, they build upon these techniques showing how to create distributable AJAX-enabled controls that include rich browser-independent JavaScript client-side functionality. The authors thoroughly explain both the JavaScript and .NET aspects of control development and how these two distinct environments come together to provide a foundation for building a rich user experience using ASP.NET AJAX.

Create object-oriented cross-browser JavaScript that supports .NET style classes, interfaces, inheritance, and method overloading
Work with components, behaviors, and controls, and learn how they relate to DOM elements.

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