All the replies pertained to only the first question and hardly anyone answered the second! Have you started writing Metro apps? If yes, which technology are you using - HTML5+WinJS, C#+XAML, or some other? Have you attempted to get your app certified? Have you targeted the App Store? These are the questions we should be looking at now... In my case, it's yes only to the first and am using XAML+C#. Still a work in progress.

I reproduced your code but it works fine here without any issues. Have you inserted this code inside a resources tag? Eg:

Code Project rocks. Although I registered some years ago, I didn't get active on the site until recently. I realize it's entirely my loss that I wasnt active earlier, when I see the richness of knowledge and expertise that abounds here. How much I could have grown had I stuck around CP! *sigh* Better late than never, I guess. Kudos to Chris and the entire CP team for making CP rock.

Viewbox is supported in Silverlight 4 so you cant use it directly in Silverlight 3. If you want to use it in version 3, then you will need to use the Silverlight Toolkit. -Mamta

Do you have Visual Web Developer installed? When you install VS 2010, it includes this but in case you have chosen a different mode of install and omitted the Visual Web developer then it could be an issue. Do check and see. -Mamta