In March of 2007, Microsoft unveiled Silverlight 1.0 in Beta and started a new chapter

for .NET programmers. That chapter is still being written as this book goes to print,

though with the release of Silverlight 2.0 Beta 1 in March of 2008the shape of Silverlight

and its potential impact is much easier to see.

There are now five distinct technologies within .NET for writing applications, and they

form a spectrum from entirely server-side to entirely client side:

• ASP.NET

• ASP.NET with AJAX

• Silverlight (potentially integrated with ASP.NET or ASP.NET with AJAX)

• Windows Forms

• Windows Presentation Foundation (WPF)

The sweet spot for most developers is in the center: applications delivered through the

browser, but ones that also provide a very rich, interactive, responsive experience for the

user. Microsoft now offers two technologies to accomplish this: AJAX and Silverlight.

AJAX is, in truth, not a new technology at all; it is the aggregation of mature technologies

in new ways (JavaScript and XML delivered asynchronously) supplemented by

some very cool well-tested code written by Microsoft (the AJAX libraries) and others.

AJAX has the advantage in that it runs on any browser that supports industry standard

protocols.

Silverlight, on the other hand, requires a browser plug-in that the user has to accept.

That plug-in contains a carefully chosen subset of the CLR, allowing Silverlight applications

to use managed code languages like VB.NET or C# and to implement applications

built on a subset of XAML, the mark up language used byWPF(and Work Flow).

The net result is that Silverlight applications are

that are simply not possible with AJAX, but they are limited to running (at the time

of this writing) on IE, Firefox, Safari on Windows, the Mac, and Linux.

Learning Silverlight is not hard, but there is quite a bit to it. A full discussion would be

a book in itself (see

[O’Reilly]).

There may come a time when Silverlight is as much a part of every ASP.NET programmer’s

skill set as AJAX is today, but we’re not quite there yet, and to keep this book at

a manageable size, we’ve decided to defer a full discussion of Silverlight for now. To

learn more, take a look at

extensive material available at