You need store all persons, something like that:
class Program
{
static List<Person> persons = new List<Person>();
static void Main(string[] args)
{
Person Luke = new Person();
Luke.Update("Luke", 15);
Console.WriteLine(Luke.ToString());
Person Daniel = new Person();
Daniel.Update("Daniel", 14, "Jones");
Console.WriteLine(Daniel.ToString());
Person Aimee = new Person();
Aimee.Update("Aimee", 18, "Jones");
Console.WriteLine(Aimee.ToString());
Person Will = new Person();
Will.Update("William", 22, "Rae");
Console.WriteLine(Will.ToString());
persons.Add(Luke);
persons.Add(Daniel );
persons.Add(Aimee );
persons.Add(Will );
var founded = FindPersonById("xxx-x-xxxxx");
Console.ReadLine();
}
static Person FindPersonById(int Id)
{
return persons.FirstOrDefault(p => p.ID == Id);
}
}