Append child from XPathNavigator : XPath « XML « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. XML
3. XPath

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Xml;
using System.Xml.XPath;

    public class MainClass
    {
        public static void Main()
        {
            XmlDocument doc;
            XPathNavigator editor2;
            XmlWriter writer;

            doc = new XmlDocument();
            doc.Load("pubs.xml");

            foreach(XPathNavigator editor in doc.CreateNavigator().Select("/pubs/titles[authors/@au_lname='Green']"))
            {
                editor2 = editor.SelectSingleNode("authors[@au_lname!='Green']");
                if (editor2!=null) editor2.DeleteSelf();
                
                writer = editor.AppendChild();
                writer.WriteStartElement("authors");
                writer.WriteAttributeString("au_lname", "A");
                writer.WriteAttributeString("au_fname", "B");
                writer.Close();
            }
            doc.Save("output.xml");
        }
    }