XAttribute

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;

class Program
{
    static void Main()
    {
        XElement lastName = new XElement("name", "James");
        lastName.Add(new XComment("It is a name"));

        XElement customer = new XElement("customer");
        customer.Add(new XAttribute("id", 123));
        customer.Add(new XElement("firstname", "Joe"));
        customer.Add(lastName);

        Console.WriteLine(customer.ToString());
    }
}