Turns out that WinRT's ability to save settings throws an exception when you try to store an enumeration value. MSDN says on the page ["Accessing app data with the Windows Runtime"](http://msdn.microsoft.com/en-us/library/windows/apps/xaml/hh464917.aspx) that only ["Runtime Data Types"](http://msdn.microsoft.com/en-us/library/windows/apps/xaml/br205768.aspx) are supported. 

So, how do you save an enum?