Notifications while app is closed in xamarin forms

I have this code working perfect in a windows phone app http://msdn.microsoft.com/en-us/library/windowsphone/develop/hh202967(v=vs.105).aspx
I would like to use it in xamarin forms (using dependecy service f required)
But my app crash in the line:

        // Try to find the push channel.
         pushChannel = HttpNotificationChannel.Find(channelName);

And I just have this error in the output screen

A first chance exception of type 'System.UnauthorizedAccessException' occurred in Microsoft.Phone.ni.dll
A first chance exception of type 'System.UnauthorizedAccessException' occurred in mscorlib.ni.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in mscorlib.ni.dll

Any solution?