The name "Binding" does not exist in the namespace

[LucaFagan]

Hello,

I've downloaded the sample, I get the flollowing error when compiling:

Severity	Code	Description	Project	File	Line	Suppression State
Error	XDG0008	The name "Binding" does not exist in the namespace "clr-namespace:CalcBinding;assembly=CalcBinding".	WpfExample	C:\Users\Luca\Desktop\Librerie WPF\CalcBinding-master\WpfExample\FifthPage.xaml	1