you add an already parented node to a second parent, the node is automatically deep-cloned.
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;
class Program
{
static void Main()
{
var address = new XElement("address",new XElement("street", "Main St"), new XElement("town", "New York"));
var customer1 = new XElement("customer1", address);
var customer2 = new XElement("customer2", address);
customer1.Element("address").Element("street").Value = "Another St";
Console.WriteLine(customer2.Element("address").Element("street").Value);
}
}
The output:
Main St