using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Collections; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Person turing = new Person("Alan Turing", new DateTime(1912, 6, 3), new DateTime(1954, 6, 7)); Person knuth = new Person("Donald Knuth", new DateTime(1938, 1, 10), null); Console.ReadKey(); } class Person { DateTime birth; DateTime? death; string name; public TimeSpan Age { get { if (death == null) { return DateTime.Now - birth; } else { return death.Value - birth; } } } public Person(string name,DateTime birth, DateTime? death) { this.birth = birth; this.death = death; this.name = name; } } } }