How to apply Validation on Xamarin.Forms??

[Quico20]

I'm trying to follow you sample applying in it to a Xamarin.Forms app but, in the Xaml code I havent been able to find this property: ValidatesOnDataErrors=True

it just doesnt exist on xamarin, so how do you make the validation warnings appear in a Xamarin.Forms app?? where do i retreive them?