Question

我的应用程序需要将客户当前年龄调整为+0.5（如果距离他们的上一个生日已有6个月）。

代码看起来应该是这样的，但是6个月内会有多少个滴答？

if (DateTime.Today - dateOfBirth.Date > new TimeSpan(6))
        {
            adjust = 0.5M;
        }
        else
        {
            adjust = 0M;
        }

提前致谢

Answer 1

编辑：你知道吗，其实？很明显，你真正需要的只是在6个月内显示用户的年龄，这就是你应该做的。

static decimal GetApproximateAge(DateTime dateOfBirth) {
    TimeSpan age = DateTime.Now - dateOfBirth;

    /* a note on the line below:
     * treating 182.5 days as equivalent to 6 months,
     * reasoning that this will provide acceptable accuracy
     * for ages below ~360 years
     * 
     * (result will be 1 day off for roughly every 4 years;
     * for a calculation of half-years to be inaccurate
     * would take 4 [years] * ~90 [days] = ~360)
     */

    // get age in units of 6 months
    // desired behavior is not to add 0.5 until
    // a full six months have elapsed since the user's last birthday --
    // using Math.Floor to ensure this
    double approxAgeInHalfYears = Math.Floor(age.TotalDays / 182.5);

    // now convert this to years
    // did it this way to restrict age to increments of 0.5
    double approxAgeInYears = approxAgeInHalfYears * 0.5;

    return Convert.ToDecimal(approxAgeInYears);
}

上述代码包括一个大的评论，解释了自己的缺点，大卫帮助指出。

现在，这里还有另一个选项。它有点难看，因为它使用循环;但它也更加坚如磐石，因为它使用了DateTime.AddMonths方法，该方法的优点是已经过Microsoft的测试和记录。

static decimal GetApproximateAge(DateTime dateOfBirth) {
    DateTime now = DateTime.Now;

    int birthYear = dateOfBirth.Year;
    int lastYear = now.Year - 1;

    // obviously, if the user's alive, he/she had a birthday last year;
    // therefore he/she is at least this old
    int minimumAgeInYears = lastYear - birthYear;

    // now the question is: how much time has passed since then?
    double actualAgeInYears = (double)minimumAgeInYears;

    // for every six months that have elapsed since the user's birthday
    // LAST year, add 0.5 to his/her age
    DateTime birthDateLastYear = new DateTime(lastYear, 1, 1)
        .AddDays(dateOfBirth.DayOfYear);

    DateTime comparisonDate = birthDateLastYear
        .AddMonths(6);

    while (comparisonDate < now) {
        actualAgeInYears += 0.5;
        comparisonDate = comparisonDate.AddMonths(6);
    }

    return Convert.ToDecimal(actualAgeInYears);
}

人们一直建议检查dateOfBirth.AddMonths(6)这个想法错误。由于dateOfBirth是日期时间，它代表用户的出生日期，而不是他们的出生日。

您要检查的是自用户上次生日以来已过去六个月 - 而不是他们出生的日期。这是一种方法：

DateTime lastBirthDay = GetLastBirthday(dateOfBirth);

if (DateTime.Today > lastBirthDay.AddMonths(6))
{
    adjust = 0.5M;
}
else
{
    adjust = 0M;
}

DateTime GetLastBirthday(DateTime dateOfBirth)
{
    int currentYear = DateTime.Now.Year;
    int birthMonth = dateOfBirth.Month;
    int birthDay = dateOfBirth.Day;

    // if user was born on Feb 29 and this year is NOT a leap year,
    // we'll say the user's birthday this year falls on Feb 28
    if (birthMonth == 2 && birthDay == 29 && !IsLeapYear(currentYear))
        birthDay = 28;

    DateTime birthdayThisYear = new DateTime(
        currentYear,
        birthMonth,
        birthDay
    );

    if (DateTime.Today > birthdayThisYear)
        return birthdayThisYear;
    else
        return birthdayThisYear.AddYears(-1);
}

bool IsLeapYear(int year) {
    return year % 400 == 0 || (year % 4 == 0 && year % 100 != 0);
}

Answer 2

为什么不if (dateOfBirth.Date.AddMonths(6) < DateTime.Today)呢？

Answer 3

        long ticks = new DateTime(0).AddMonths(6).Ticks;
        TimeSpan ts = new TimeSpan(ticks);

Answer 4

if (dateOfBirth.Date.AddMonths(6) < DateTime.Today)
{
   age += 0.5;
}

Answer 5

我认为你可能会使事情过于复杂：

DateTime displayDate = User.BirthDate; // User.BirthDate is a mock for however you get the birth date

if(DateTime.Now.AddMonths(-6) > displayDate)
{
    // More than 6 Months have passed, so perform your logic to add .5 years
}

Answer 6

这样的东西？

if (DateTime.Now.AddMonths(-6) > dateofBirth.Date)
{
    dateOfBirth = dateOfBirth.AddMonths(6);
}

Answer 7

我想你真的想知道自从他们的上一个生日以来是否是半年而不是六个月（因为月份的长度不同）。

    int daysDiff = DateTime.Now.DayOfYear - dayofBirth.DayOfYear;
    if (daysDiff <0) daysDiff += 365;
    double adjust = daysDiff > 365/2 ? 0.5 : 0.0;

Answer 8

DateTime today = DateTime.Today;
DateTime lastBirthday = dateOfBirth.Date.AddYears(today.Year - dateOfBirth.Year);
if (lastBirthday > today) lastBirthday = lastBirthday.AddYears(-1);

if (today > lastBirthday.AddMonths(6))
    adjust = 0.5M;
else
    adjust = 0M;

确定c＃生日以来是否已经过了6个月

8 个答案: