using System;

using System.Xml.Linq;

​

public static class Program

{

    public static void Main(string[] args)

    {

        XNamespace xsi = "http://www.w3.org/2001/XMLSchema-instance";

​

        var doc = new XDocument(

            new XElement("ranzcp_user",

                new XAttribute(XNamespace.Xmlns + "ns1", "urn:logon"),

                new XAttribute(XNamespace.Xmlns + "xsi", xsi),

                new XElement("user_id", 12345678,

                    new XAttribute(xsi + "type", "xsd:string")

                    )

                )

            );

​

        Console.WriteLine(doc);

    }

}

​

​

​