Beginning Web Development, Silverlight, and ASP.NET AJAX

354
CHAPTER 15 ■ ENHANCING THE WEB EXPERIENCE WITH SILVERLIGHT
}
}
return ro;
And this only differentiates between Internet Explorer and Firefox. If you are not
writing an Ajax application, but one that uses a non-ubiquitous technology such as CSS
or DHTML, you are left querying the user agent and trusting that the server returns an
honest answer. The user agent string is simply a text field that contains what the server
believes the browser that is communicating with it is. It is relatively easy to overwrite, and
thus, a browser from a mobile device (which doesn’t support CSS) could be spoofed into
thinking that it is Internet Explorer, and incompatible data would be delivered to it.
It’s pretty clear that HTML and scripting, while incredibly useful, are reaching the
end of their serviceable lives with the growing expectations of users for richer and more
dynamic applications. With that in mind, platform vendors have offered a number of
technologies that enhance what HTML can do, with examples being things like Java
applets, ActiveX controls, and Flash movies.
A new technology in 2007—and one that has a number of unique and distinct value
propositions that make it a compelling one—is Microsoft Silverlight.
Introducing Silverlight
In Chapter 8, you looked at Windows Presentation Foundation (WPF) and a new technology
that it provides called Extensible Application Markup Language (XAML). This
language allows a UI and all its interactions to be defined with simple XML markup tags.
This empowers a separation of design and development, so that the designer can become
an integral part of the development process.
In the past, a designer would make a mock-up, or “comp,” of the desired vision for
the web site or application. This might be a set of wireframe drawings, pictures, simple
animations, or scribbles on a piece of paper. The developer would have to take these
visions and implement them, constrained by what the technology would permit. The
result was often disappointing for both parties.
With XAML, the designer can use tools (such as the Microsoft Expression suite) to
design the graphics, interactions, animations, and media that they desire to have in the
site, and the developer can simply take this XAML and “activate” it by writing the code
behind it that allows it to be used as an application.
Thus, the designer and the developer are working from a common set of artifacts,
allowing next-generation designer-centric experiences to not just be possible, but to be
relatively easy to implement.
Silverlight is a plug-in for the browser that renders XAML and exposes a programming
model in JavaScript. Thus, web developers have a new suite of tools and technologies in
XAML that will allow them to take their sites to the next level of richness, but they still