17. 適用前 メインルーチン public void Main () { var user = new User (DateTime.Now); Console.WriteLine("あなたの年齢は " + user.Age.ToString() + " です。"); user.Save (user); } 18. USER USER CLASS public class User { private DateTime _birthday; public User (DateTime birthday) { _birthday = birthday; } public int Age{ get { GetAge (); } } private int GetAge(){ // 計算 return 9; // 永遠の9歳 } public void Save(){ var repogito