WPF MarkupExtension

  public class IsBiggerNumberExtension : MarkupExtension
    {
        public IsBiggerNumberExtension(object num)
        {
            Number = num;
        }
         public object Number
        {
            get;
            set;
        }
        public IsBiggerNumberExtension()
        {

        }
        public override object ProvideValue(IServiceProvider serviceProvider)
        {
            var target = serviceProvider.GetService(typeof(IProvideValueTarget)) as IProvideValueTarget;

            var dp = target.TargetProperty as DependencyProperty;

            var dpo = target.TargetObject as DependencyObject;

            double d = 0,d2=0;

            var n = double.TryParse(dpo.GetValue(dp).ToString(),out d);

            var n1= double.TryParse(Number.ToString(), out d2);

            var result = d>d2;

            var h = dp.IsValidType(result);

            return h?result:(object)result.ToString();
        }
    }

<TextBlock Grid.Row="1"  Text="{local:IsBiggerNumber 1}" >