Jack @ ASP.NET

Google Web Toolkit (GWT) is a development toolkit for building and optimizing complex browser-based applications. Its goal is to enable productive development of high-performance web applications without the developer having to be an expert in browser quirks, XMLHttpRequest, and JavaScript. GWT is used by many products at Google, including Google Wave and the new version of AdWords. It’s open source, completely free, and used by thousands of developers around the world.

The GWT SDK provides a set of core Java APIs and Widgets. These allow you to write AJAX applications in Java and then compile the source to highly optimized JavaScript that runs across all browsers, including mobile browsers for Android and the iPhone.

Constructing AJAX applications in this manner is more productive thanks to a higher level of abstraction on top of common concepts like DOM manipulation and XHR communication.

You aren’t limited to pre-canned widgets either. Anything you can do with the browser’s DOM and JavaScript can be done in GWT, including interacting with hand-written JavaScript.

It’s important to understand the difference between server-centric “AJAX” and client “pure” AJAX.

In server-centric AJAX applications, even though the application leverages asynchronous calls between client and server, the server is the one that is actually responsible for generating the necessary HTML content before providing it to the client. This leads to heavy bandwidth usage, and lack of responsiveness. In addition, the client application becomes far too reliant on the functionality of the server, and its ability to provide good markup, as opposed to simply requiring data and simple interaction.

In client AJAX applications, the communication with the server is purely for passing data back and forth. All of the rendering and state is maintained within the client environment, and the server is only brought into the picture as needed.

So, “The server should only be concerned with data, not presentation”.

In order to enable our ability to easily create dynamic UI and place the rendering process on the client, we need a way to define templates of markup that represent the UI we wish to create, and allow the runtime to instantiate them for us. This alleviates the need to write a bunch of DOM code or depend on server-rendering.

If you’ve used WebForms before, you’re already familiar with the approach many of its server controls take. You have access to a set of properties that allow you to define arbitrary templates of content, complete with HTML, server controls, and data binding expressions. This model makes it very easy to create dynamic UI that is rendered server-side [Advance Animation].

ASP.NET AJAX 4.0 introduces the ability to define templates as well, but purely client-side. Now you can create the HTML markup you want to use for representing your template, complete with HTML and data binding expressions. In this example, we’ve created an unordered list template whose content is a list item whose content is the value of the Name property of the JSON object that is bound to it. The data binding expression resembles that of WPF.

Earlier today the ASP.NET team launched a new Microsoft Ajax CDN (Content Delivery Network) service that provides caching support for AJAX libraries (including jQuery and ASP.NET AJAX).  The service is available for free, does not require any registration, and can be used for both commercial and non-commercial purposes.

What does a CDN provide?

Content delivery networks (CDNs) are composed of "edge cache" servers that are strategically placed around the world at key Internet network points.  These "edge cache" servers can be used to cache and deliver all types of content – including images, videos, CSS and JavaScript files.

Using a CDN can significantly improve a website’s end-user performance, since it enables browsers to more quickly retrieve and download content.  For example, instead of having a browser request for an image traverse all the way across the Internet to your web server to download, a CDN can instead serve the request directly from a nearby "edge cache" server that might only be a single network hop away from your customer (making it return much faster – which makes your pages load quicker). 

Summary

The Microsoft Ajax CDN enables you to significantly improve the performance of ASP.NET Web Forms and ASP.NET MVC applications that use ASP.NET AJAX or jQuery.  The service is available for free, does not require any registration, and can be used for both commercial and non-commercial purposes.

ASP.NET 4.0 will make it especially easy for ASP.NET Web Forms developers to take advantage of the CDN. By setting one property of the ScriptManager control, you will be able to redirect all requests for the built-in ASP.NET JavaScript files to the CDN and improve the performance of your Web Forms applications.