score:3

Accepted answer

Assuming Gregorian calendar, "first day" week rule and that the first day of the week is Monday.

First day week rule:

Indicates that the first week of the year starts on the first day of the year and ends before the following designated first day of the week

int firstDayOfWeek = (int)DayOfWeek.Monday;
var q = 
    from u in TblUsers
    let date = u.CreateDate.Value
    let num = date.DayOfYear - 1
    let num2 = ((int)date.DayOfWeek) - (num % 7)
    let num3 = ((num2 - firstDayOfWeek) + 14) % 7
    let week = (((num + num3) / 7) + 1)
    group u by week into g
    select new 
    {
        Week = g.Key,
        Count = g.Count ()
    };

score:0

Hope this helps:

    var d1 = new DateTime(1990, 1, 1);
    var d2 = new DateTime(1990, 1, 2);
    var d3 = new DateTime(1990, 1, 11);
    var d4 = new DateTime(1990, 1, 12);

    var records = new[] { 
        new { date = d1, freq = 1 }, 
        new { date = d2, freq = 2 }, 
        new { date = d3, freq = 3 }, 
        new { date = d4, freq = 4 } 
    };

    //ticks * WeekDays * DayHours * HourMins * MinSecs
    var weekTicks = (Int64)10000000 * 7 * 24 * 60 * 60;   
    var res = records.GroupBy(x => x.date.Ticks / weekTicks)
             .Select(x => new { week=x.Key ,sum=x.Sum(y=>y.freq)});

And this is the result:

[0] = { week = 99085, sum = 3 }

[1] = { week = 99086, sum = 7 }


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