using System;

using System.Linq;

using System.Xml.Linq;

​

public class Program

{

    public static void Main(string[] args)

    {

        const string xml = @"<?xml version=""1.0"" encoding=""utf-8""?>

<soapenv:Envelope xmlns:soapenv=""http://schemas.xmlsoap.org/soap/envelope/"" xmlns:xsd=""http://www.w3.org/2001/XMLSchema"" xmlns:xsi=""http://www.w3.org/2001/XMLSchema-instance"">

    <soapenv:Body>

        <generateSSOResponse xmlns=""http://url.com"">

            <generateSSOReturn>2DKtjZNq58THggh42lNsGvgGTjF8RSBA</generateSSOReturn>

        </generateSSOResponse>

    </soapenv:Body>

</soapenv:Envelope>";

​

        var doc = XDocument.Parse(xml);

​

        XNamespace ns = "http://url.com";

        var token = (string) doc .Descendants(ns + "generateSSOReturn").Single();

        Console.WriteLine(token);

    }    

}