XML extension methods

using System.Globalization;
using System.Xml.Linq;

namespace Demo.Utility
{
    public static class XmlUtilites
    {
        public static string ElementValue(this XElement element, string childName, string defaultValue = null)
        {
            if (element == null) return defaultValue;

            var child = element.Element(childName);
            return child != null ? child.Value : defaultValue;
        }

        public static double ElementDoubleValue(this XElement element, string childName, CultureInfo cultureInfo = null)
        {
            if (element == null) return defaultValue;

            var culture = cultureInfo ?? CultureInfo.InvariantCulture;
            var child = element.Element(childName);
            return child != null && !string.IsNullOrEmpty(child.Value) ? double.Parse(child.Value, culture) : double.NaN;
        }

        public static decimal ElementDecimalValue(this XElement element, string childName, CultureInfo cultureInfo = null)
        {
            if (element == null) return defaultValue;

            var child = element.Element(childName);
            var culture = cultureInfo ?? CultureInfo.InvariantCulture;
            return child != null && !string.IsNullOrEmpty(child.Value)
                       ? decimal.Parse(child.Value, culture)
                       : 0;
        }
    }
}