在Linq to SQL中按周分组(周数)

Range variable name can be inferred only from a simple or qualified name with no arguments

LINQ to SQL 不支持 Calendar.WeekOfYear 方法,但您可能会创建一个TSQL function that wraps the call to DatePart

var x = from F in DB.T
        group F by new {Year = F.Date.Year, Week = Math.Floor((decimal)F.Date.DayOfYear / 7)} into FGroup
        orderby FGroup.Key.Year, FGroup.Key.Week
        select new {
            Year = FGroup.Key.Year,
            Week = FGroup.Key.Week,
            Count = FGroup.Count()
        };

Year    Week    Count
2004    46      3
2004    47      3
2004    48      3
2004    49      3
2004    50      2
2005    0       1
2005    1       8
2005    2       3
2005    3       1
2005    12      2
2005    13      2

你可以用 SqlFunctions.DatePart 方法从 System.Data.Entity.SqlServer 命名空间。

// Return the week number
From F In DB.T Group R By SqlFunctions.DatePart("week", F.Date)

这是正确的。

from F in DB.T group F by F.Date.DayOfYear / 7;

F.Date.DayOfYear / 7 . 每个对象都是T中满足组条件的对象的集合。

如果您关心您在以下代码中所处的文化,则会考虑到这一点:

var ci = CultureInfo.CurrentCulture;
var cal = ci.Calendar;
var rule = ci.DateTimeFormat.CalendarWeekRule;
var firstDayOfWeek = ci.DateTimeFormat.FirstDayOfWeek;

var groups = from F in DB.T
             group F by cal.GetWeekOfYear(F, rule, firstDayOfWeek) into R
             select R;

首先你应该知道一周中第一天的日期。

得到一周中第一天的日期。 您可以使用以下代码:

public static class DateTimeExtensions
{
    public static DateTime StartOfWeek(this DateTime dt, DayOfWeek startOfWeek)
    {
        int diff = dt.DayOfWeek - startOfWeek;
        if (diff < 0)
        {
            diff += 7;
        }
        return dt.AddDays(-1 * diff).Date;
    }
}

因此,在常规SQL中:

SELECT * From T GROUP BY DATEPART(wk, T.Date)

T.GroupBy(i => i.Date.StartOfWeek(DayOfWeek.Monday));