missing an assembly reference???? error

Question

Severity Code Description Project File Line Suppression State
Error CS0234 The type or namespace name 'XamlFilePathAttributeAttribute' does not exist in the namespace 'Xamarin.Forms.Xaml' (are you missing an assembly reference?) Popups c:\users\mic24user\documents\visual studio 2015\Projects\Popups\Popups\Popups\obj\Debug\Popups.App.xaml.g.cs 14 Active