Beginning Web Development, Silverlight, and ASP.NET AJAX

CHAPTER 11 ■ AJAX APPLICATIONS AND EMPOWERING THE WEB USER EXPERIENCE 277
}
currentPic--;
ShowPic(currentPic);
function DoNext()
{
currentPic++;
ShowPic(currentPic);
}
This technique and methodology will prove very useful when you’re building your
applications. It also introduces a whole new way of thinking about the user experience.
Forward caching changes the way in which many applications (e.g., maps) can be presented
to the user. If you are building an application that could make the most of this, it’s
well worth thinking it through and building it into your site.
Summary
In this chapter, you took a look at Ajax, seeing some examples of applications where Ajax
greatly improves the overall user experience, such as MSN MoneyCentral and Google
Maps. You looked at the history of dynamic, partial page refresh technologies, leading up
to the XMLHttpRequest object, for which the technique of Ajax was coined.
You looked into the architecture of Ajax and how you can use the XMLHttpRequest
object in code, before delving into a couple of examples. The first example, though very
simple, demonstrated straightaway that the instant-feedback nature of Ajax (as opposed
to the traditional delayed-via-postback feedback of a web application) can improve your
end users’ experience.
You then looked into another major technique used by Ajax programmers: forward
caching. This technique is used by applications such as mapping applications to allow
users to get what seems to be instant access to data. Applications using this technique
are smart enough to download and cache data that would likely be requested next. When