create XElement with namespace

XElementNamespace.cs

    public static string ParameterXml
    {
        get
        {
            XNamespace xsd = "http://www.w3.org/2001/XMLSchema";
            XNamespace xsi = "http://www.w3.org/2001/XMLSchema-instance";
            XNamespace rs = "http://schemas.microsoft.com/sqlserver/2006/03/15/reporting/reportingservices";


            XElement root = new XElement("ScheduleDefinition",
                                new XAttribute(XNamespace.Xmlns + "xsd", "http://www.w3.org/2001/XMLSchema"),
                                new XAttribute(XNamespace.Xmlns + "xsi", "http://www.w3.org/2001/XMLSchema-instance"),
                                new XElement(rs + "StartDateTime", "time_time_time"),
                                new XElement(rs + "MonthlyRecurrence",
                                        new XElement(rs + "Days", "1,3-6"),
                                        new XElement(rs + "MonthsOfYear"))
            );

            root.Descendants(rs + "MonthsOfYear").First().Add(
                            new XElement(rs + "Feb", "true") );

            Console.WriteLine();
            return root.ToString();
        }
    }