Getting Started with Silverlight
In addition to browser differences, the graphical capabilities of HTML are too limiting for many user experiences that people want to create. Drawing a simple line, incorporating video, and a number of other things are extremely difficult or impossible with HTML alone. It's not that these technologies were poorly designed, but simply that they were designed for hyperlinked documents rather than the extremely rich presentations that most people want to create on the Web these days.
Considering these issues, it's no wonder that Adobe Flash has been so successful. Whether someone wants to create a professionally designed website, an online game (or any number of other applications), or even a simple advertisement, Flash has been a natural choice for escaping the limitations of HTML. If you doubt the pervasiveness of Flash, try this experiment: Think of a brand of food you eat, and then navigate to the brand's website. Chances are you'll find Flash content at your destination. (I just tried pepsi.com, doritos.com, and oscarmayer.com, and all three are using Flash at the time of writing.) The Flash development experience leaves much to be desired, however. Flash (the runtime environment, as well as the tool) suffers from the same basic problem as HTML: Many people are trying to use it for creating rich applications, but it was originally designed for something else (in this case, simple animations).
This is why the introduction of Silverlight is so exciting. A promising alternative to Flash, Silverlight enables the creation of rich web content and applications using a lightweight add-on that is friendly to both designers and developers. Yes, the first version of Silverlight is primitive in areas, but it's a true development platform based on concepts and APIs introduced with Windows Presentation Foundation (WPF) in 2006 and in development for many years prior. And, unlike just about any software that has come out of Microsoft, Silverlight is a small download! Version 1.0 is less than 1.5MB, so users who don't have it can get it pretty quickly when browsing to Silverlight content. (By default, Silverlight also automatically updates to later versions when they are available.) Silverlight might just be the silver bullet many designers and developers have been waiting for.
FAQ: What are the differences between Silverlight and Adobe Flash?
"Flash" is the name for both a runtime component and a design tool. "Silverlight" refers to a runtime component only, but there are both design tools (such as Expression Blend) and development tools (such as Visual Studio) for Silverlight. For years, Flash has been the only viable option for rich web-based content, and now Silverlight is positioned to fill the same need. The two technologies have similar features, but there are naturally pros and cons to each.
The biggest thing Flash (the runtime component) has going for it is ubiquity. A website can use Flash with confidence that the vast majority of viewers already have the necessary player installed. Silverlight, on the other hand, is brand new and will take some time to spread dependent on the amount of compelling Silverlight content out in the wild. Of course, both Flash and Silverlight are designed to have a quick and painless installation, so sites don't have to inconvenience users too much if they don't have the necessary software. But even if Silverlight spreads like wildfire during the first few months, the Flash runtime component can still reach places that Silverlight can't (yet), such as mobile devices.
Flash has a variety of visual features that Silverlight lacks, such as bitmap effects (blurring and glowing) and shape tweening (morphing the shape of an object in an animation). Notable features of Silverlight that Flash lacks are higher quality video (even HD 720p full-screen with reasonable hardware) with VC-1 codecs included, seamless interaction with HTML, support for high-resolution and pressure-sensitive input data from a stylus or touch device, and content that's more discoverable to search engines by default thanks to the use of XML rather than compiled script.
The biggest advantage of Silverlight over Flash is in the design of the platform and its associ-ated tools. This advantage becomes especially apparent if you're building an interactive appli-cation rather than a simple piece of content. Flash (the design tool) has a huge learning curve for creating an application with even a small amount of logic, and the resulting code is often quite unnatural (and hard to debug). But most software developers, or even people who dabble with HTML and a little bit of programming, should find the learning curve for Silverlight to be pretty small. And if you happen to already be familiar with WPF, learning Silverlight is a breeze.
FAQ: What are the differences between Silverlight and WPF?
Whereas Silverlight is designed for creating rich web content or applications that can be viewed in multiple browsers and multiple operating systems, WPF is designed for creating rich Windows applications. WPF applications require the .NET Framework 3.0 or later, which is a much larger download than Silverlight, although Windows Vista and later operating systems already have it installed by default.
Silverlight 1.0 is essentially a subset of WPF, although Silverlight also has a few unique pieces related to video, on-demand downloading of any content, and the control that hosts the content inside a web page. Some WPF features missing from Silverlight 1.0 are common user interface controls (such as buttons and scrollbars), layout panels, 3D graphics, data binding, rich document support, performance optimizations from hardware accelerated graph-ics, and more. In addition, Silverlight 1.0 applications don't have the benefit of the depth and breadth of the .NET Framework APIs, unless you use them from server-side ASP.NET code. The next version of Silverlight will close some of the gap between Silverlight and WPF, but it will undoubtedly always remain a subset of what WPF and the full .NET Framework provide.
WPF doesn't only support Windows applications, but also applications that run inside the browser called XAML Browser Applications (XBAPs). XBAPs can arguably be considered web applications because their content renders seamlessly inside the browser similar to Silverlight content. However, XBAPs require the .NET Framework 3.0 or later, so they only run on Windows (and only then if the .NET Framework is installed) and only work inside Internet Explorer and Firefox. (Furthermore, Firefox support requires the .NET Framework 3.5 or later.) XBAPs support a much larger subset of WPF functionality than Silverlight 1.0, so they can be an appropriate choice for creating very rich applications that are web-like in their deployment.
For example, the British Library has an application called "Turning the Pages" that takes advantage of WPF 3D graphics inside the browser.
FAQ: What is the relationship between Silverlight 1.0 and the prerelease version of Silverlight?
It's a bit unusual that the next version of Silverlight (currently labeled 1.1) has been available in a prerelease form before Silverlight 1.0 was even finished, but as the version number suggests, it simply is the next version of Silverlight. This next version is a superset of Silverlight 1.0 and is still a subset of WPF and the .NET Framework (but with some unique features of its own). The most notable additions planned for the next version of Silverlight are
Despite all this, everything you learn about Silverlight 1.0 is directly applicable to future versions of Silverlight.
FAQ: What web server is required for serving Silverlight content?
Any web server will do, although be sure to set up the MIME type for .xaml files. Using Windows Server can give additional benefits when it comes to streaming media, such as the Faststream technology in Windows Media Services. Silverlight Streaming by Windows Live can also be an attractive option for hosting Silverlight content on someone else's web server. It supports scalable streaming free (if you don't mind advertise-ments being served with your content) or for a small fee.
FAQ: What are the differences between Silverlight for Windows, Silverlight for Mac OS X, and Silverlight for Linux?
Silverlight supports the same feature set, because it is designed to be completely compatible between all the operating systems and browsers it supports. One advantage Silverlight has on Windows is the ability to get high-resolution and pressure-sensitive input data from a stylus or touch device, although this extra information is given in a way that avoids the need to write Windows-specific code. (See Chapter 7, "Responding to Input Events," for more details.) Silverlight also has different performance characteristics on different browsers and operating systems. For example, windowless controls (described later in the chapter) and elements with transparency are especially slow in Safari on Mac OS X. And of course, Silverlight has bugs that only apply to a specific browser or operating system. Some of these are pointed out in this book.