using System;

using System.IO;

using System.Xml;

using System.Xml.XPath;

public class Program

{

    public static void Main()

    {

        string str = @"<props>

  <username>dervis.kayimbasioglu</username>

</props>";

        var result = XPathExtractor.Extract(str, "/props/username");

        Console.WriteLine(result);

    }

​

}

​

public static class XPathExtractor 

{

    public static object Extract(string input, string xpath)

    {

        string result;

        using (StringReader sr = new StringReader(input))

        using (XmlReader reader = XmlReader.Create(sr))

        {

            XPathDocument document = new XPathDocument(reader);

            XPathNavigator navigator = document.CreateNavigator();

            XPathNodeIterator iterator = navigator.Select(xpath); 

            iterator.MoveNext();

            result = iterator.Current.Value;

        }

        return result;

    }

}

​