var address = new XElement ("address",
new XElement ("street", "Lawley St"),
new XElement ("town", "North Beach")
);
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); // Lawley St