Extensions.cs

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using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;
 
namespace System.Xml.XPath;
 
public static class Extensions
{
    public static XPathNavigator CreateNavigator(this XNode node)
    {
        return node.CreateNavigator(null);
    }
 
    public static XPathNavigator CreateNavigator(this XNode node, XmlNameTable? nameTable)
    {
        if (node == null)
        {
            throw new ArgumentNullException("node");
        }
        if (node is XDocumentType)
        {
            throw new ArgumentException(System.SR.Format(System.SR.Argument_CreateNavigator, XmlNodeType.DocumentType));
        }
        if (node is XText xText)
        {
            if (xText.GetParent() is XDocument)
            {
                throw new ArgumentException(System.SR.Format(System.SR.Argument_CreateNavigator, XmlNodeType.Whitespace));
            }
            node = CalibrateText(xText);
        }
        return new XNodeNavigator(node, nameTable);
    }
 
    public static object XPathEvaluate(this XNode node, string expression)
    {
        return node.XPathEvaluate(expression, null);
    }
 
    public static object XPathEvaluate(this XNode node, string expression, IXmlNamespaceResolver? resolver)
    {
        if (node == null)
        {
            throw new ArgumentNullException("node");
        }
        return default(XPathEvaluator).Evaluate<object>(node, expression, resolver);
    }
 
    public static XElement? XPathSelectElement(this XNode node, string expression)
    {
        return node.XPathSelectElement(expression, null);
    }
 
    public static XElement? XPathSelectElement(this XNode node, string expression, IXmlNamespaceResolver? resolver)
    {
        return node.XPathSelectElements(expression, resolver).FirstOrDefault();
    }
 
    public static IEnumerable<XElement> XPathSelectElements(this XNode node, string expression)
    {
        return node.XPathSelectElements(expression, null);
    }
 
    public static IEnumerable<XElement> XPathSelectElements(this XNode node, string expression, IXmlNamespaceResolver? resolver)
    {
        if (node == null)
        {
            throw new ArgumentNullException("node");
        }
        return (IEnumerable<XElement>)default(XPathEvaluator).Evaluate<XElement>(node, expression, resolver);
    }
 
    private static XText CalibrateText(XText n)
    {
        XContainer parent = n.GetParent();
        if (parent == null)
        {
            return n;
        }
        foreach (XNode item in parent.Nodes())
        {
            if (item is XText result && item == n)
            {
                return result;
            }
        }
        return null;
    }
}