Question

我有一个列表dateHolder，它具有DateTime数据类型并保存数百个DateTime值。该列表从最旧的值累积到最新值。这是一个功能：

private void CheckQuarter()
{
    int lastPoint = dateHolder.Count(); //Has dates from 4/12/2015 to 30/11/2017
    DateTime startDate = dateHolder(0); //startDate = 4/12/2015
    DateTime endDate = dateHolder(lastPoint - 1); //endDate = 30/11/2017
}

从上面的代码示例中，我想根据仅限日期和月份检查某些日期的发生。我对年份价值不感兴趣。我想检查的日期和月份值是：

1st Jan
31st Mar
1st Apr
30th Jun
1st Jul
30th Sep
1st Oct
31st Dec

从上述日期和月份值中，您可能会看到我正在检查季度值。现在，在startDate和endDate内，如何查看我提到的那些日期？非常感谢...

Answer 1

LINQ Enumerable.Count您可以使用an overload that takes a predicate。例如如果你只关心月和日：

var yourTargetDates = new List<DateTime>()
{
    new DateTime(1, 1, 1), // Jan 1st
    new DateTime(1, 3, 31), // March 31st
    ... // etc
};

var occurrences = dateHolder.Count(d => yourTargetDates.Any(td => td.Month == d.Month && td.Day == d.Day));

你可能仍然需要在某些日期和时间周围迎合怪异，尽管在处理日期和时间时通常会这样。

Answer 2

我找到了一种方法来实现它。这是功能：

private void CheckQuarter()
{
    int lastPoint = dateHolder.Count();
    DateTime startDate = dateHolder(0);
    DateTime endDate = dateHolder(lastPoint - 1);
    DateTime CurrD = startDate;
    while ((CurrD <= endDate))
    {
        if ((CurrD.Month == 1 && CurrD.Day == 1))  //1st Jan
        {
            //Do your process
        }
        else if ((CurrD.Month == 3 && CurrD.Day == 31))  //31st Mar
        {
            //Do your process
        }
        else if ((CurrD.Month == 4 && CurrD.Day == 1))  //1st Apr
        {
            //Do your process
        }
        else if ((CurrD.Month == 6 && CurrD.Day == 30))  //30th Jun
        {
            //Do your process
        }
        else if ((CurrD.Month == 7 && CurrD.Day == 1))  //1st July
        {
            //Do your process
        }
        else if ((CurrD.Month == 9 && CurrD.Day == 30))  //30th Sep
        {
            //Do your process
        }
        else if ((CurrD.Month == 10 && CurrD.Day == 1))  //1st Oct
        {
            //Do your process
        }
        else if ((CurrD.Month == 12 && CurrD.Day == 31))  //31st Dec
        {
            //Do your process
        }
        else
        {
           //Do your process
        }

        CurrD = CurrD.AddDays(1);
    }
}

这是实现目标的一种方法。但是，我认为有一种更简单的方法需要更少的编码才能做到这一点。

检查一个时间跨度内的日期和月份出现次数

2 个答案: