Question

我有一个名为PaymentFrequency的枚举类型，其值表示每年有多少付款... 所以我有

public enum PaymentFrequency
{
    None             = 0,
    Annually         = 1,
    SemiAnnually     = 2,
    EveryFourthMonth = 3,
    Quarterly        = 4,
    BiMonthly        = 6,
    Monthly          = 12,
    EveryFourthWeek  = 13,
    SemiMonthly      = 24,
    BiWeekly         = 26,
    Weekly           = 52
}

根据NumberOfPayments，PaymentFrequency和FirstPaymentDate（类型为DateTimeOffset），我想计算LastPaymentDate。但是，我有一个问题，想知道在SemiMonthly的情况下要添加多少时间单位（天，月）......

    switch (paymentFrequency)
    {
        // add years...
        case PaymentFrequency.Annually:
            LastPaymentDate = FirstPaymentDate.AddYears(NumberOfPayments - 1); 
            break;
        // add months...
        case PaymentFrequency.SemiAnnually:
            LastPaymentDate = FirstPaymentDate.AddMonths((NumberOfPayments - 1) * 6); // 6 months
            break;
        case PaymentFrequency.EveryFourthMonth:
            LastPaymentDate = FirstPaymentDate.AddMonths((NumberOfPayments - 1) * 4); // 4 months
            break;
        case PaymentFrequency.Quarterly:
            LastPaymentDate = FirstPaymentDate.AddMonths((NumberOfPayments - 1) * 3); // 3 months
            break;
        case PaymentFrequency.BiMonthly:
            LastPaymentDate = FirstPaymentDate.AddMonths((NumberOfPayments - 1) * 2); // 2 months
            break;
        case PaymentFrequency.Monthly:
            LastPaymentDate = FirstPaymentDate.AddMonths(NumberOfPayments - 1);
            break;
        // add days...
        case PaymentFrequency.EveryFourthWeek:
            LastPaymentDate = FirstPaymentDate.AddDays((NumberOfPayments - 1) * 4 * 7); // 4 weeks (1 week = 7 days)
            break;
        case PaymentFrequency.SemiMonthly:
            // NOTE: how many days in semi month? AddMonths (0.5) does not work :)
            LastPaymentDate = FirstPaymentDate.AddMonths((NumberOfPayments - 1) * 0.5); // 2 weeks (1 week = 7 days)
            break;
        case PaymentFrequency.BiWeekly:
            LastPaymentDate = FirstPaymentDate.AddDays((NumberOfPayments - 1) * 2 * 7); // 2 weeks (1 week = 7 days)
            break;
        case PaymentFrequency.Weekly:
            LastPaymentDate = FirstPaymentDate.AddDays((NumberOfPayments - 1) * 7); // 1 week (1 week = 7 days)
            break;
        case PaymentFrequency.None:
        default:
            throw new ArgumentException("Payment frequency is not initialized to valid value!", "paymentFrequency");
    }

那么，使用SemiMonthly时我应该使用多少天/几个月？如果不知道每个月的确切天数，这是否可能？或者这真的很简单，我刚用完了咖啡因而且我没有看到森林的树木：）

Answer 1

对于半月刊，如果您的第一笔付款始终是该月的第一笔付款（也就是说，从第1日到第13日的任何时间，从第13次开始是有问题的，如评论中所述），您可以这样做如下：

 // assuming first payment will be 1st of month, add month for every 2 payments
 // num payments / 2 (int division, remainder is chucked)
 // then add 15 days if this is even payment of the month
 LastPaymentDate = FirstPaymentDate.AddMonths((NumberOfPayments - 1) / 2)
     .AddDays((NumberOfPayments % 2) == 0 ? 15 : 0);

因此，对于第一次付款，这将添加0个月和0天，因此是第一个付款日期。对于第二次付款，这将增加0个月（int dividision，其余被清除）和15个月的16个月。对于第三次付款，这将增加下个月1日的1个月（1/3）和0天等等。

这假设FirstPaymentDate将在某个月的第一天。如果你想让第16个成为开始日期等，你可能会看到从这里去的地方等。

有意义吗？

所以说明一下，如果我们有：

DateTime LastPaymentDate, FirstPaymentDate = new DateTime(2011, 12, 5);

for(int numOfPayments=1; numOfPayments<=24; numOfPayments++)
{
    LastPaymentDate = FirstPaymentDate.AddMonths((numOfPayments - 1) / 2)
        .AddDays((numOfPayments % 2) == 0 ? 15 : 0);

    Console.WriteLine(LastPaymentDate);
}

这个循环会给我们：

12/5/2011 12:00:00 AM
12/20/2011 12:00:00 AM
1/5/2012 12:00:00 AM
// etc...
10/20/2012 12:00:00 AM
11/5/2012 12:00:00 AM
11/20/2012 12:00:00 AM

Answer 2

因为月份的长度各不相同，所以您不能只添加预定义的数字。你必须知道你正在处理哪个月，并从那里开始。

如果你知道一个月的第一个和第十六个是截止日期，那么最后一笔付款是12月16日（假设你正在计算一个日历年）。

Answer 3

半月付款的基本配对是：

1和16（一个月的第1天和第16天）
15和（2 | 3）？（本月15日和最后一天）

偷看并选择

Answer 4

我最近遇到了同样的问题，但我需要允许任何日期输入。这有点乱，需要重构，但这是我到目前为止所提出的。二月有一些我不得不破解的问题。

Date returnDate;

if (numberOfPayments % 2 == 0)
{
   returnDate = date.AddMonths(numberOfPayments / 2);

    if (date.Day == DateTime.DaysInMonth(date.Year, date.Month))//Last day of the month adjustment
    {
        returnDate = new Date(returnDate.Year, returnDate.Month, DateTime.DaysInMonth(returnDate.Year, returnDate.Month));
    }
}
else
{
    returnDate = date.Day <= 15 ? date.AddDays(15).AddMonths((numberOfPayments - 1) / 2) : date.AddDays(-15).AddMonths((numberOfPayments + 1) / 2);
    if (date.Day == DateTime.DaysInMonth(date.Year, date.Month))//Last day of the month adjustment
    {
        returnDate = new Date(returnDate.Year, returnDate.Month, 15);
    }
    else if (date.Month == 2 && date.Day == 14)
    {
        returnDate = returnDate.AddMonths(-1);
        returnDate = new Date(returnDate.Year, returnDate.Month, returnDate.Month == 2 ? 28 : 29);
    }
    else if (date.Month == 2 && date.Day == 15)
    {
        returnDate = returnDate.AddMonths(-1);
        returnDate = new Date(returnDate.Year, returnDateMonth, DateTime.DaysInMonth(returnDate.Year, returnDate.Month));
    }
}

return returnDate;

为“半月刊”添加多少天

4 个答案: