C# XPath search

gistfile1.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.XPath;
using System.IO;

namespace StudyCSharp
{
    class Program
    {
        static void Main(string[] args)
        {
            string xmlText = "<root>" + 
    "<a href=\"/PatternFramework/Pages/LogOut.aspx?np=/sites/novatestsite/Home.aspx\" slick-uniqueid=\"92\">Sign out</a>" + 
    "</root>";
            XPathNavigator nav; 
            XPathDocument docNav; 
            XPathNodeIterator NodeIter;
            String strExpression;
            docNav = new XPathDocument(new StringReader(xmlText));
            nav = docNav.CreateNavigator();
            strExpression = "//a[contains(lower-case(@href), \"logout.aspx\")]";//xpath 2.0, c# not support
            strExpression = "//a[contains(translate(@href, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'),'logout.aspx')]";//xpath 1.0
            NodeIter = nav.Select(strExpression);
            while(NodeIter.MoveNext())
            {
                Console.WriteLine("href={0}", NodeIter.Current.GetAttribute("href", ""));
            }
        }
    }
}