C#中的可空類型

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 public class Person {        public DateTime birth;        public DateTime? death;        string name;        public TimeSpan Age {            get {                if (!death.HasValue) {                    return DateTime.Now - birth;                }                else {                    return death.Value - birth;                }            }        }        //建構函式        public Person(string name, DateTime birth,DateTime?death) {            this.birth = birth;            this.death = death;            this.name = name;        }    }Person tr = new Person("AAAA", new DateTime(1988, 12, 13),null);            Person kk = new Person("BBBB", new DateTime(1912, 12, 13), new DateTime(1954, 12, 12));            Console.ReadKey();

　　

C#中的可空類型