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The Manifold Blunders of Xaml–Part 1: Version and Platform Hell

I started work with “Xaml-based” platforms in the pre-Beta days of WPF, so I’ve been working with this technology longer than most. Back then I was utterly awed and inspired by it’s capabilities. Today I’m frustrated and sometimes outraged. As I’ve traveled to various conferences, worked with various companies and interacted with the many Caliburn.Micro users, I’ve discovered that I’m not the only one who feels this way. This blog series attempts to catalog a number of the issues, some of which have been there from the very beginning; others creeping in over time. This is an aggregate of my own observations and those of the community.


Let’s take a brief stroll through the platform timeline:

  • 2006 – WPF 3.0
  • 2007 – Silverlight 1
  • 2007– WPF 3.5
  • 2008 – Silverlight 2
  • 2008 – WPF3.5 sp1
  • 2009 – Silverlight 3
  • 2010 - Silverlight 4
  • 2010 – WP7
  • 2010 – WPF4.0
  • 2011 – Silverlight 5
  • 2011 – WP7 Mango
  • 2011 – Lakeshore1
  • 2012 – WinRT/Metro2

If we focus on the platforms and ignore their various versions, we have something like this:

  • 2006 – WPF
  • 2007 Silverlight 1.0 (no CLR)
  • 2008 – Silverlight 2.0 (CLR)
  • 2010 – WP7
  • 2011 – Lakeshore
  • 2012 – WinRT/Metro

So, it appears that Microsoft has released a new UI platform at least every two years! Let’s contrast that to the timeline for pre-Xaml UI technologies:

  • 1985?– Win16
  • 1995 – Win32
  • 2001 – WinForms
  • 2006 – WPF

Interesting. We have at least 5 – 6 years between platforms prior to Xaml, but it’s actually about 10yrs due to the fact that WinForms is just making Win32 available to managed languages. It’s just a wrapper around existing APIs. Each of the Xaml platforms is actually a different runtime altogether. So as far as platforms go, we’ve gone from one every 10yrs to one every 2 years. But that’s not all, let’s look at Xaml itself:

  • 2006 – Xaml 2006 Spec
  • 2008 – Silverlight 1 Xaml
  • 2009 – Xaml 2009 Spec
  • 2011 – Silverlight 5 Xaml
  • 2012 – WinRT/Metro Xaml

Aside from the actual platforms released, we have a parallel divergence in Xaml markup capabilities. In 2006 the first version of Xaml was released. It was formally defined and released as a spec shortly after. When Silverlight came along, Microsoft failed to create a Xaml language compatible with their own specification. In fact, even Silverlight 5 doesn’t comply with the Xaml 2006 spec. In 2009 Microsoft released a new version of Xaml that fixed several important shortcomings with the 2006 spec….but not a single platform implemented it. WP7 is still playing catch-up with Silverlight and WPF. WinRT/Metro Xaml has less Xaml features than any platform. Furthermore, it significantly changes some aspects of Xaml altogether, making it compatible with almost nothing. Furthermore, some of the changes they are making will prevent it from ever becoming compatible in the future.

When I step back and try to look at this information objectively, the most natural conclusion I can come to is that Microsoft UI technologies are, and have been for the last five years, in a state of complete instability…and it doesn’t show any signs of change (esp. with the rumors that WP8 will not use Silverlight, but some variant of WinRT). You can’t count on anything. If we forget about app developers for a moment, and think about the ecosystem, imagine the effect this has on third party products, control vendors, open source frameworks and tooling. Every time MS spits out a new platform or Xaml flavor, the entire ecosystem has to start over.

My own Experience

I first wrote Caliburn for WPF when there was no word on anything like Silverlight existing. When Silverlight was first announced, it was branded WPF/e so I thought my framework would port. Unfortunately, when SL2 was made available, there were so many differences that I had no choice but to completely re-write Caliburn. Then, when WP7 was announced, I started porting Caliburn to that, only to discover that it was not possible. So, I did another complete re-write resulting in Caliburn.Micro. Now we have WinRT/Metro. I think I can port it, albeit, with a ton of conditional code. But, I’m not 100% sure yet. If it looks like another re-write…I’m done with this game.

Maintenance and Innovation

There are lots of negative side-effects to this sort of instability. The one that hits me most is that it creates a battle between maintenance and innovation. Again, speaking of my own project, I have plenty of ideas about how to improve Caliburn.Micro. I think some of them are minor niceties, but others are more along the innovative lines. But, you will never see any of them come to fruition. Why? Because the instability of the underlying platform, the constant release of new platforms…has put my project into a state of perpetual maintenance. I can’t innovate because I’m still trying to deal with the differences in WP7.5 and I’ve got developers (who can blame them?) banging down my door wanting to know when WinRT/Metro version will be available. It’s been discussed much in recent years as to why innovation seams to happen in non-Microsoft open source and on other platforms like Mac…while very little happens in Windows software. Could it be because we are spending our time re-writing everything every two years? and don’t have time to develop anything forward thinking?

Careless and Arbitrary

Sadly, many of the API and Xaml differences were completely avoidable. I remember one particular bug I had in Caliburn. It resulted from the fact that List<T>.Remove was implemented differently between WPF and Silverlight. In a particular scenario it would work fine on one platform and crash your app on another. There are hundreds, probably thousands of such issues, from the BCL all the way up through the UI stack.  We aren’t talking about missing features here. We are talking about the same features which exhibit different behavior or have altered APIs.  Sure, Microsoft worked hard to improve this with successive releases of Silverlight. But then came WP7, which stepped us back in time. Now look at WinRT. There are a number of changes that are completely arbitrary. They serve no technical purpose and don’t improve the API. They just make more work for developers who want to port code. If you want another fine example, just try to write a cross-framework design mode check.

A Lack of Understanding

Sigh. This one perfectly ironic issue really troubles me sometimes. Through all of this, I’ve realized that Microsoft doesn’t understand their own platform. I’ve got more to say on this later, but let’s look at this from an API perspective here. Consider this: every control specific to WP7 development could have been built on top of Silverlight without a need for a modified runtime. Most controls could have been implemented simply by styling an existing control or applying a template. For example, the Pivot control can be implemented using a tab control with a custom template and some attached behaviors. In fact, wouldn’t it have been cool if you could just use a Tab control in WP7 and it just changed it’s appearance to work on the phone?! Wait, wasn’t that the idea behind templating and adaptive layout to begin with? Here’s another example: Behaviors. Perhaps you didn’t know that Microsoft built this twice? In WPF there were Triggers. In fact, in both WPF and the Blend behavior system, there is a class called TriggerBase. They have the same name! They do the same thing! But, you can’t create custom triggers or actions in WPF because the ctor is marked internal. Did it not occur to anyone that they should just remove that instead of re-inventing the wheel? As a result, we now have two methods of doing triggers, and you have to know which to use for what. It’s even true in Silverlight, which has limited support for “traditional” triggers, but does have some. Ridiculous. I could go on and on about the types of internal and cross-platform inconsistencies MS has created by not simply understanding the core capabilities of their own framework.

All of this get’s really interesting if you consider that Mac is the platform that is considered most cutting edge and innovative in terms of UX…and they’ve scarcely had any major breaking changes since 2002. Considering that their phone apps run on their tablet and they are porting a number iOS features back to OSX…it must be nice only having to worry about two platforms and knowing that the OS vendor is making a visible, tangible effort to unify those two platforms…..but I’m getting off topic now.

End of Part One

There are lots of problems with Xaml, but I chose to start this series with one of my particular pain points. Some developers neither care nor are affected (yet) by these sorts of version issues, but they have a big effect on the surrounding ecosystem and are going to be with us for the next decade. Over the next several blog posts, we’ll discuss many other problems, some technical, some not so much, but all have been singled out by multiple members of the community (read: not just me) as problems. It is my hope that Microsoft employees working on these technologies will read this and seriously consider what they can do to improve things going forward or at least not perpetuate the same mistakes again. I also hope that .NET developers will take a long, hard look at this part of the platform and make an honest valuation of its strengths and weaknesses.


1. Lakeshore is the name I’ve been hearing thrown around for the Xaml-runtime for XBox, which sources say is Silverlight-based, but drastically altered. I have no official word from Microsoft on this. It’s just what I heard through the grapevine, though I’m fairly confident in the accuracy of the information. Supposedly this is what is powering the “apps” in the new XBox dashboard which was released around last Thanksgiving.  EDIT: Apparently the XBox version is called Lakeview not Lakeshore.

2. I don’t actually know when WinRT/Metro will be released. I imagine that 2012 is a reasonable guess.

Posted 04-18-2012 11:43 AM by Rob Eisenberg


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