public class PersonValidator : EnhancedAbstractValidator<PersonViewModel>
{
   public PersonValidator()
   {
   	RuleForProp(a => a.FirstName)
   		.NotNull();
   } 
}

[FluentValidation.Attributes.Validator(typeof(PersonValidator))]
public class PersonViewModel : AbstractValidationViewModel
{
   public ValidatableProperty<string> FirstName { get; set; } = new ValidatableProperty<string>();
}

   public class PersonPage : ContentPage
   {
       public PersonPage()
       {
           BindingContext = new PersonViewModel();

   		//Here we pass in the name of the property we would like this control to bind to. 
           var firstNameControl = new ValidatableEntryControl(nameof(PersonViewModel.FirstName));

           var sl = new StackLayout()
           {
               Orientation = StackOrientation.Vertical
           };

           sl.Children.Add(firstNameControl);
   		
           var submitButton = new Button()
   		{
   			Text = "Submit"
   		};

   		//Sample to trigger validator, normally you would call the validator from within your view model.
           submitButton.SetBinding(Button.CommandProperty, nameof(PersonViewModel.ValidateCommand));

           sl.Children.Add(submitButton);

           this.Content = sl;
       }

   }