SymbolIcon is not supported in WPF project

I am trying to use the SymbolIcon (as defined here: http://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.xaml.controls.symbolicon.aspx ) in my XAML code. But the XAML will not compile stating "SymbolIcon is not supported in WPF project".

Can anyone tell me if any additional assembly is missing to use SymbolIcon. I have the "Segoe UI Symbol" font on my box.

Thanks, RDV