Validating Number Input for a UWP XAML TextBox

Int.cs

namespace MyApp
{
    public sealed class Int
    {
        public static readonly DependencyProperty AttachedProperty = DependencyProperty.RegisterAttached(
            "IntAttached", typeof(bool), typeof(Int), null);

        public static readonly DependencyProperty ValueProperty = DependencyProperty.RegisterAttached(
            "Value", typeof(int), typeof(Int), new PropertyMetadata(null, OnAttach));

        public static readonly DependencyProperty ValidateProperty = DependencyProperty.RegisterAttached(
            "Validate", typeof(Func<int, bool>), typeof(Int), null);

        static void OnAttach(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            var textbox = sender as TextBox;
            if (textbox == null || (bool) textbox.GetValue(AttachedProperty)) return;

            textbox.SetValue(AttachedProperty, true);

            textbox.InputScope = new InputScope();
            textbox.InputScope.Names.Add(
                new InputScopeName(InputScopeNameValue.Number)
            );

            Brush _background = null;

            textbox.Loaded += (ls, le) =>
            {
                var validate = GetValidate(textbox);

                textbox.TextChanging += (stc, etc) =>
                {
                    if (_background == null)
                        _background = textbox.Background;

                    if (int.TryParse(textbox.Text, out int value)
                        && (validate == null || validate(value)))
                    {
                        SetValue(textbox, value);
                        textbox.Background = _background;
                    }
                    else
                    {
                        textbox.Background = new SolidColorBrush(Colors.LightPink);
                    }
                };
            };
        }

        public static Func<int, bool> GetValidate(DependencyObject dependencyObject)
        {
            return (Func<int, bool>) (dependencyObject.GetValue(ValidateProperty) ?? int.MinValue);
        }

        public static void SetValidate(DependencyObject sender, Func<int, bool> value)
        {
            sender.SetValue(ValidateProperty, value);
        }

        public static int GetValue(DependencyObject dependencyObject)
        {
            return (int) (dependencyObject.GetValue(ValueProperty) ?? default(int));
        }

        public static void SetValue(DependencyObject sender, int value)
        {
            sender.SetValue(ValueProperty, value);
            ((TextBox) sender).Text = value.ToString();
        }
    }
}

UsageView.xaml

<UserControl
    x:Class="MyApp.UsageView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="using:MyApp"
    mc:Ignorable="d"
    d:DesignHeight="300"
    d:DesignWidth="400">

    <Grid>
      <TextBox 
        local:Int.Value="{x:Bind Model.Width, Mode=TwoWay}"
        local:Int.Validate="{x:Bind ValidateWidth, Mode=OneWay}"/>

    </Grid>
</UserControl>

UsageView.xaml.cs

namespace MyApp
{
    public sealed partial class UsageView : UserControl
    {
        public static readonly DependencyProperty CropProperty
            = DependencyProperty.Register("Model", typeof(MyModel), typeof(UsageView),
                new PropertyMetadata(default(MyModel)));

        public CropView()
        {
            InitializeComponent();
        }

        public Func<int, bool> ValidateWidth
        {
            get
            {
                return value => value > 0
                                && value < 1000;
            }
        }
    }
}