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;            }        }    }}