Lazy XML selection, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Xml;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            {
                var doc = CreateDocument();
                var selection = doc.SelectNodes("root/elem[@n < 4]");
                PrintAndModify(selection);
            }
            
            {
                var doc = CreateDocument();
                var selection = doc.SelectNodes("root/elem[@n < 4]");
                Console.WriteLine("Selected " + selection.Count + " elements");
                PrintAndModify(selection);
            }
        }
        
        private static XmlDocument CreateDocument() {
            var doc = new XmlDocument();
            var root = doc.CreateElement("root");
            doc.AppendChild(root);

for (var i = 0; i < 10; i++)
            {
                var elem = doc.CreateElement("elem");
                elem.SetAttribute("n", i.ToString());
                root.AppendChild(elem);
            }
            
            return doc;
        }
        
        private static void PrintAndModify(XmlNodeList xnl) {
            var i = 0;
            foreach (XmlElement elem in xnl){
                Console.WriteLine("Seen element: " + elem.OuterXml);
                var next = elem.NextSibling;
                if (next == null) { continue; }
                var nextNext = (XmlElement)next.NextSibling;
                if (nextNext != null)
                {
                    nextNext.SetAttribute("n", elem.GetAttribute("n"));
                }
            }
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,19 sec, absolute running time: 0,22 sec, cpu time: 0,2 sec, average memory usage: 20 Mb, average nr of threads: 4, absolute service time: 0,43 sec