MS.Internal.Xml.XPath.Query.Advance C# (CSharp) Method

        public abstract XPathNavigator Advance();

        private double Number(XPathNodeIterator nodeIterator)
        {
            if (arg == null)
            {
                return(XmlConvertEx.ToXPathDouble(nodeIterator.Current.Value));
            }
            object argVal = arg.Evaluate(nodeIterator);

            switch (GetXPathType(argVal))
            {
            case XPathResultType.NodeSet:
                XPathNavigator value = arg.Advance();
                if (value != null)
                {
                    return(Number(value.Value));
                }
                break;

            case XPathResultType.String:
                return(Number((string)argVal));

            case XPathResultType.Boolean:
                return(Number((bool)argVal));

            case XPathResultType.Number:
                return((double)argVal);

            case XPathResultType_Navigator:
                return(Number(((XPathNavigator)argVal).Value));
            }
            return(double.NaN);
        }