多少天添加“半月” [英] How many days to add for "semi-monthly"

问题描述

我有一个名为 PaymentFrequency 的枚举类型，其值表示每年要支付多少付款...
所以我有

I have a enum type called PaymentFrequency whose values indicate how many payments per year are being made... So I have

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）I想计算 LastPaymentDate 。但是，如果是SemiMonthly ...，我有问题要解决添加多少时间单位（天，月）...

Based on NumberOfPayments, PaymentFrequency, and FirstPaymentDate (of type DateTimeOffset) I want to calculate LastPaymentDate. But I am having issue figuring out how many time units (days, months) to add in case of SemiMonthly...

    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，在使用SemiMonthly时应该使用多少天/月？
这是甚至可能没有知道每个月的确切天数？
或者这真的很简单，我刚刚跑出咖啡因，我没有看到树林：）

So, how many days/months should I use when using SemiMonthly? Is this even possible without knowing exact # of days for each month in between? Or is this really simple, and I have just run out of caffeine and I am not seeing forest for the trees :)

推荐答案

对于半月，如果您的第一笔付款总是本月的第一笔付款（也就是说，从第1到第13，从第13页开始，从评论中讨论的问题，您可以做）如下：

For Semi-Monthly, if your first payment was always the 1st payment of the month as well (that is, anytime from the 1st to the 13th, starting after 13th is problematic as discussed in the comments), you could do as follows:

 // 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);

所以对于第一笔付款，这将添加0个月和0天，这是第一个付款日期。对于第二次付款，这将增加0个月（int分割，剩余部分被卡住）和15个月的16个月。对于第三笔付款，这将在下个月1日添加1个月（1/3）和0天。

So for the 1st payment, this will add 0 months and 0 days so be 1st payment date. For 2nd payment, this will add 0 months (int dividision, remainder is chucked) and 15 days for 16th of month. For 3rd payment, this will add 1 month (1 / 3) and 0 days for 1st of next month, etc.

这是假设FirstPaymentDate将在某一个月的第一。你可能会看到从这里去哪里，如果你想允许第16个开始日期等。

This is assuming that the FirstPaymentDate will be on the 1st of some given month. You can probably see where to go from here if you want to allow the 16th to be a starting date, etc.

有意义吗？

因此，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);
}

此循环将给我们：

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

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