Can't Parse XML from XRDS document
Response.Write(xmlDoc.SelectSingleNode("/xrds/XRD").InnerXml);  //Parse it - failed
Response.Write(xmlDoc.SelectSingleNode("/XRD").InnerXml);       //failed

System.Xml.XmlDocument xmlDoc = new System.Xml.XmlDocument();
string gtest = "<?xml version="1.0" encoding="UTF-8"?><xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)"><XRD><Service priority="0"><Type>http://specs.openid.net/auth/2.0/server</Type><Type>http://openid.net/sreg/1.0</Type> <URI>https://www.mydomain.com/login</URI></Service></XRD></xrds:XRDS>";
xmlDoc.LoadXml(gtest);//Load data into the xml.
Response.Write(xmlDoc.SelectSingleNode("/xrds/XRD").InnerXml);//Parse XML
	
xmlDoc.GetElementsByTagName("XRD")[0].InnerXml

xmlDoc.DocumentElement.ChildNodes[0].InnerXml
	
XmlDocument xmlDoc = new XmlDocument();
        string gtest = "<?xml version="1.0" encoding="UTF-8"?><xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)"><XRD><Service priority="0"><Type>http://specs.openid.net/auth/2.0/server</Type><Type>http://openid.net/sreg/1.0</Type> <URI>https://www.mydomain.com/login</URI></Service></XRD></xrds:XRDS>";
        xmlDoc.LoadXml(gtest);//Load data into the xml.
        XmlNodeList nodeList = xmlDoc.GetElementsByTagName("XRD");
        foreach (XmlNode node in nodeList)
        {
            Console.Write(node.InnerXml);
        }
	
XmlNamespaceManager nsmgr = new XmlNamespaceManager(xmlDoc.NameTable);
Response.Write(xmlDoc.SelectSingleNode("/xrds:XRDS/XRD",nsmgr).InnerXml);