Question

我正在尝试从数据库中获取日期的一周，并将其与DateTimePicker中的用户选择值进行比较。我的用户可以选择一天，我写了一个类，以1到52的形式给我当天的那一周。我试图选择获取LINQ来比较数据库中给定日期的周数和由用户。例如：

var report = (from orders in Context.Orders
              where DateEx.ISOWeekNumber(orders.Date) == 
                    DateEx.ISOWeekNumber(datepicker1.Value)
              select orders);

但它根本不起作用，因为LINQ没有ISOWeekNumber的翻译。谁知道我怎么能这样做？

Answer 1

之类的东西呢？

Math.Truncate(date.DayOfYear/7) +1

给你：

var report = (from orders in Context.Orders
    where Math.Truncate(orders.Date.DayOfYear/7) + 1 ==
    Math.Truncate(datepicker1.Value.DayOfYear/7) + 1
    select orders);

希望有所帮助，

丹

可能将Math.Truncate（date.DayOfYear / 7）带入新的DateEx类

Answer 2

您可以编写一个完全符合您需要的C＃方法。关于LINQ的一个好处是，在编写查询时，如何使用完整编程语言的所有工具。

谷歌快速搜索“isoweeknumber c＃”了：

private int weekNumber(DateTime fromDate)
{
    // Get jan 1st of the year
    DateTime startOfYear = fromDate.AddDays(- fromDate.Day + 1).AddMonths(- fromDate.Month +1);
    // Get dec 31st of the year
    DateTime endOfYear = startOfYear.AddYears(1).AddDays(-1);
    // ISO 8601 weeks start with Monday
    // The first week of a year includes the first Thursday
    // DayOfWeek returns 0 for sunday up to 6 for saterday
    int[] iso8601Correction = {6,7,8,9,10,4,5};
    int nds = fromDate.Subtract(startOfYear).Days  + iso8601Correction[(int)startOfYear.DayOfWeek];
    int wk = nds / 7;
    switch(wk)
    {
        case 0 :
            // Return weeknumber of dec 31st of the previous year
            return weekNumber(startOfYear.AddDays(-1));
        case 53 :
            // If dec 31st falls before thursday it is week 01 of next year
            if (endOfYear.DayOfWeek < DayOfWeek.Thursday)
                return 1;
            else
                return wk;
        default : return wk;
    }
}

来源：http://codebetter.com/blogs/peter.van.ooijen/archive/2005/09/26/132466.aspx

Answer 3

我使用了System.Globalization命名空间中的Calendar.GetWeekOfYear。

MSDN Link

        DateTimeFormatInfo dfi = DateTimeFormatInfo.CurrentInfo;
        DateTime specifiedDate = DateTime.Now;
        Calendar cal = dfi.Calendar;
        int weekNo = cal.GetWeekOfYear(specifiedDate, dfi.CalendarWeekRule, dfi.FirstDayOfWeek);
        var dataForWeek = data.Where(x => cal.GetWeekOfYear(x.DeliveryDate.Value, dfi.CalendarWeekRule, dfi.FirstDayOfWeek) == weekNo);

从linq查询获取约会周

3 个答案: