I'm really enjoying these tutorials...

I haven't been able to figure out a problem I'm having on step 15 of task 3 of exercise 3 (Adding an Application Bar).  When trying to set the value of the SystemTray dependency property, I get the compiler error: The name 'SystemTray' does not exist in the current context.  Is anyone else having this problem, or have any idea what I might be doing wrong?  Is SystemTray called something new in the April Refresh?

 

***RESOLVED!*** I had to of course add using Microsoft.Phone.Shell to MainPage.xaml.cs.  (This step is missing from the tutorial.)