public object Convert(object[] values,
                              Type targetType,
                              object parameter,
                              CultureInfo culture)
        {
            ThicknessConverter conv = new ThicknessConverter();
            string             thickStr;
            Thickness          thickness;

            if (values[0] != null)
            {
                if (values.Length >= 3)
                {
                    thickStr = values[2] as string;
                    if (conv.IsValid(thickStr))
                    {
                        thickness = (Thickness)conv.ConvertFromString(thickStr);
                        return(thickness);
                    }
                }
            }
            else
            {
                thickStr = values[1] as string;
                if (conv.IsValid(thickStr))
                {
                    thickness = (Thickness)conv.ConvertFromString(thickStr);
                    return(thickness);
                }
            }

            return(new Thickness(0));
        }