reset on error

[JohanLarsson]

    public class ValueControl : Control
    {
        public static readonly DependencyProperty ValueProperty = DependencyProperty.Register(
            "Value",
            typeof(int),
            typeof(ValueControl),
            new FrameworkPropertyMetadata(
                default(int),
                FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
                null,
                CoerceValue));

        private bool isResetting;

        static ValueControl()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(ValueControl), new FrameworkPropertyMetadata(typeof(ValueControl)));
            EventManager.RegisterClassHandler(typeof(ValueControl), Validation.ErrorEvent, new EventHandler<ValidationErrorEventArgs>(OnError));
        }

        public int Value
        {
            get { return (int)this.GetValue(ValueProperty); }
            set { this.SetValue(ValueProperty, value); }
        }

        private static object CoerceValue(DependencyObject d, object basevalue)
        {
            var control = (ValueControl)d;
            if (control.isResetting)
            {
                return control.GetValue(ValueProperty);
            }

            return basevalue;
        }

        private static void OnError(object sender, ValidationErrorEventArgs e)
        {
            if (e.Action == ValidationErrorEventAction.Added)
            {
                var control = (ValueControl)sender;
                control.isResetting = true;
                BindingOperations.GetBindingExpressionBase(control, ValueProperty)?.UpdateTarget();
                control.isResetting = false;
            }
        }
    }