C# 根据出生日期（年月日）计算年龄的代码

public int GetAgeByBirthdate(DateTime birthdate)
    {
        DateTime now = DateTime.Now;
        int age = now.Year - birthdate.Year;
        if (now.Month < birthdate.Month || (now.Month == birthdate.Month && now.Day < birthdate.Day))
        {
            age--;
        }
        return age <  ?  : age;
    }