bbwy/BBWY.Client/Converters/WidthConveter.cs

using System;
using System.Globalization;
using System.Windows.Data;

namespace BBWY.Client.Converters
{
    public class WidthConveter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            if (value is double)
            {
                double.TryParse(parameter?.ToString(), out double p);
                var width = (double)value;
                if (width == 0)
                    return 0;
                return width - p;
            }
            return 0;
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}