Set a Namespace Prefix To via the XAttribute object
using System; using System.Linq; using System.Xml.Linq; using System.Collections.Generic; class Program/* w w w. j a va 2 s . c om*/ { static void Main(string[] args){ XNamespace nameSpace = "http://www.book2s.com"; XElement xBookParticipants = new XElement(nameSpace + "BookParticipants", new XAttribute(XNamespace.Xmlns + "linqdev", nameSpace), new XElement(nameSpace + "BookParticipant")); Console.WriteLine(xBookParticipants.ToString()); } }