问将用户输入限制为wpf数据网格中的正整数

EN

public class ValueConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        { return value; }

        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            if (!OnlyPositiveIntergerAllowed(value.ToString()))
            {
                string s = Regex.Replace(value.ToString(), @"[^0-9]+", string.Empty);

                if(s=="")
                return 0;
                else
                    return s;

            }
           if (value is string && (string)value == "")
            {
                return 0;
            }

            return value;

        }
        private static bool OnlyPositiveIntergerAllowed(string text)
        {
            var regex = new Regex("[^0-9]+"); //regex that matches disallowed text
            return !regex.IsMatch(text);
        }
}