Simple EmptyStringValidator Attached Property

MainPage.xaml

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:SelectionPerPlatform.Portable"
             xmlns:telerikInput="clr-namespace:Telerik.XamarinForms.Input;assembly=Telerik.XamarinForms.Input"
             x:Class="Example.Portable.MainPage">

    <telerikInput:RadEntry local:TelerikValidator.EmptyStringValidator="True"
                           VerticalOptions="Center"
                           Margin="10"/>
</ContentPage>

TelerikValidator.cs

public static class TelerikValidator
{
    public static BindableProperty EmptyStringValidatorProperty = BindableProperty.CreateAttached(
        "EmptyStringValidator", 
        typeof(bool), 
        typeof(TelerikValidator), 
        false, 
        propertyChanged: EmptyStringValidatorChanged);

    private static void EmptyStringValidatorChanged(BindableObject bindable, object oldValue, object newValue)
    {
        VisualElement radEntry = (VisualElement)bindable;

        radEntry.PropertyChanged -= Entry_PropertyChanged;

        if ((bool)newValue)
        {
            radEntry.PropertyChanged += Entry_PropertyChanged;
        }
    }

    private static void Entry_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
    {
        if (sender is RadEntry entry && e.PropertyName == RadEntry.TextProperty.PropertyName)
        {
            entry.TextChanged += Entry_TextChanged;
        }
    }

    private static void Entry_TextChanged(object sender, TextChangedEventArgs e)
    {
        if (!string.IsNullOrEmpty(e.NewTextValue))
        {
            (sender as RadEntry).WatermarkText = "";
            (sender as RadEntry).WatermarkTextColor = Color.Gray;
        }
        else
        {
            (sender as RadEntry).WatermarkText = "text cannot be empty";
            (sender as RadEntry).WatermarkTextColor = Color.Red;
        }
    }

    public static bool GetEmptyStringValidator(BindableObject bindable)
    {
        return (bool)bindable.GetValue(EmptyStringValidatorProperty);
    }

    public static void SetEmptyStringValidator(BindableObject bindable, bool value)
    {
        bindable.SetValue(EmptyStringValidatorProperty, value);
    }
}