C#中的可空类型

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;
                }
            }
        }

        public TimeSpan Age1 {
            get {
                DateTime lastAlive = death.HasValue ? DateTime.Now : death.Value;
                return birth - lastAlive;
            }
        }

        public TimeSpan Age2 {
            get {
                return (death ?? DateTime.Now) - birth;
            }
        }
        //构造函数
        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();

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