I'm just back from Microsoft's Professional Developers Conference in Los Angeles, where the star of the show was the latest update to the Silverlight browser plug-in that lets you run .NET applications cross-platform and within the browser. The pace of development is remarkable. It is only 9 months ago that we were first shown the beta of Silverlight 3, at the Mix conference in March. Silverlight 3 was fully released in July; and now we have version 4.0 beta, with release promised for the first half of 2010.
It is a big release too. Many of the top Silverlight feature requests are being implemented, including printing, right-click and mouse wheel support, a rich text control with editing, clipboard support (though text-only in the beta), drag-and-drop, interaction with Webcams and microphones, multitouch control, improved just-in-time compilation for faster performance, and improved databinding for business applications.
In addition, the forthcoming Visual Studio 2010 is the first to have the kind of Silverlight development tools you would expect, with a true visual design surface and drag-and-drop data binding. On the server, WCF (Windows Communication Foundation) RIA Services simplify the effort of authentication, talking to data, and integrating with ASP.NET.
Another notable feature is the ability to run a Silverlight application out of the browser, started from a desktop shortcut and displayed in a custom window. New in version 4.0 is an HTML control, which embeds IE on Windows and WebKit (used in Safari) on the Mac. These are desktop/web application hybrids. Silverlight 4 blurs the boundaries, by adding a new trusted mode. Subject to the user passing a security dialog, a trusted out-of-browser application gets local file access to user data, cross-domain network access, and on Windows native code interop through COM automation.
The snag with this last point is that any Silverlight application which uses COM automation will only run on Windows, breaking the cross-platform compatibility which is a key reason to use Silverlight in the first place. Although Microsoft says the feature has been put in simply to meet the requirements of a few Enterprise customers, it seems to me that it goes well beyond that, making Silverlight viable in many scenarios that previously would have required a native solution.
Microsoft's ideal scenario is one where applications run everywhere, but run best on Windows, preserving its desktop lock-in. The company calls this "lighting up the platform"; but Windows is somehow the only platform that gets lit up.
I still think it is time to learn Silverlight. The reason is not only Microsoft's signposting of this as its key technology for future client development, but something else I saw last week: Google's Chrome OS. I'll be writing more about this; but I was impressed by how this forthcoming browser-based operating system promises to solve long-standing problems: cheap, lightweight computers that are secure, that start up instantly, that give us access to all our data, but can be left in the back of a taxi without compromising our secrets.
What if Chrome OS catches on? Does Microsoft become irrelevant? The real world does not move that fast; but considering the continuing popularity of the Mac along with the prospect of Chrome OS, it strikes me as brave to presume a Windows-only client for future development. Silverlight on the other hand should run in Chrome OS, either using Mono's Moonlight, or the Intel port being done for Moblin, or perhaps Microsoft itself will have to dirty its hands with Linux. Google might block Silverlight - it was non-committal on the subject at the Chrome OS press briefing - but I'm guessing that concerns over appearing excessively controlling will trump the desire to shut out a competitor.
The point here is not that Silverlight is the answer for all client development; there are plenty of other strong choices. The point rather is that for Microsoft platform developers Silverlight is the technology that makes it possible to take your C# or VB.Net skills and transition them to a new cross-platform, web-oriented world.
At Microsoft Tech-Ed 2009 in Berlin long-time Windows server expert Mark Minasi gave a session on the .vhd format used by Microsoft for virtual hard drives in Hyper-V, the virtualisation feature built into Windows server 2008.
Minasi's talk was not about Hyper-V, but rather about other things you can do with a .VHD. He even noted that in a Windows environment you can use a .VHD as a superior form of ZIP (though without the compression), if you want a single file that can contain windows files and folders while preserving NTFS security attributes, and that can be mounted - or "attached" in .VHD jargon - rather than having to be extracted elsewhere.
One neat trick is to use .VHDs for multi-boot. Multi-boot is less important now that virtualisation works so well, but can still be useful if want to test an operating system with full performance and access to hardware such as accelerated graphics. The old way to do this is with multiple partitions, but this is somewhat inconvenient. Windows 7 is able to boot from a .VHD, and you can set up mutiple VHDs so that you can choose which one to use at start-up. There are a couple of limitations. The operating system has to be Windows 7 or presumably 2008 R2 (which uses the same kernel); and sleep/hibernate does not work in this configuration.
A VHD is still just a file, so you can back it up by copying it elsewhere, provided it is not the one currently running. Note that in this configuration only the hard drive is virtual, not the computer hardware, so while you could go on to mount the VHD in Hyper-V it would be like moving Windows to a new motherboard and very likely would not boot.
Another clever tip is that Windows 7 setup support a keystroke combination, Shift F10, which gives access to the command line for MinWin, the cut-down version of Windows that runs during setup. Here you can get access to Diskpart, the command-line disk management tool, which among other things lets you create a VHD. So you can take a machine with an untouched hard drive, boot into the Windows 7 setup, shell to the command line and create a VHD, then attach and install Windows onto that new virtual drive. Setup actually states that this does not work; but it does work, and we saw it demonstrated.
There are three kinds of VHDs. A fixed VHD has the same on-disk size as its capacity. An expanding (or dynamic) VHD reports the size that you specify when it is greated, but only occupies the space on its host that is needed by the data written there. This is convenient for backup, and lets you over-commit the host drive if you choose to. The third kind is a differencing VHD - a VHD that is based on a parent and only occupies the space needed by its difference as you write to it. The GUI Windows disk management tool does not support creation of differencing VHDs: one of Minasi's points is that you should learn the command line approach using Diskpart in order to get access to all the available features. That said, differencing VHDs are supported in the Hyper-V GUI management tool.
The bottom line is that VHDs have uses that go beyond virtual machines and if you work on the Windows platform it is well worth becoming familiar with them.
