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How to group by and sum for every 7 days using linq lambda?

I have a filtered list of results for particular month. I am working on report that should print this in excel. How to query so that I display the results in this format?
Expected format:
Date Qty Other fields
1
2
3
4
5
6
7
Total
8
9
10
11
12
13
14
Total
...
29
30
31
Total
I need to group by using lambda expression. Note: not all days of the filtered month have returned results, but I need to display all days anyway.

One way is you could do the integer division to GroupBy so that you will have value which is rounded to the nearest integer and then take the Sum per Group by Select statement:
var result = list.GroupBy(x => (x.Date - 1)/ 7)
.Select(x => x.Sum(y => y.Qty));

How to select hour in priority

I'm using C# and SQL Server 2008 R2.
I have hour data like this:
Client_ID TheHour HourMin HourMAx
53026 09:00 7 9
53026 12:00 10 12
53026 15:00 13 15
53026 18:00 16 19
I will put TheHour into my combobox, that depends on computer hour.
When the computer hour is 10:00 then the value of my combobox:
12:00
15:00
18:00
09:00
My linq is :
int The_Hour = DateTime.Now.Hour;
var query = from o in oEntite_T.LS_CLIENTHORRAIRE
where o.CLIENT_ID == CLIENT_ID &&
The_Hour >= o.HEURE_MIN && The_Hour <= o.HEURE_MAX
select o;
LesListe = query.ToList();
It return only 1 value, which is 12:00.
That meant my combobox will select hour that depend on computer hour, but it leave the possibility for the user to select another hour.

Here is a working example in LINQPad, I also added a flag to indicate selected value.:
void Main()
{
var LS_CLIENTHORRAIREs = new List<LS_CLIENTHORRAIRE>
{
new LS_CLIENTHORRAIRE{TheHour="09:00",HourMin=7,HourMAx=9},
new LS_CLIENTHORRAIRE{TheHour="12:00",HourMin=10,HourMAx=12},
new LS_CLIENTHORRAIRE{TheHour="15:00",HourMin=13,HourMAx=15},
new LS_CLIENTHORRAIRE{TheHour="18:00",HourMin=16,HourMAx=19}
};
LS_CLIENTHORRAIREs.Dump();
int The_Hour = 10;
var query = from o in LS_CLIENTHORRAIREs
select new {o.TheHour,o.HourMin,o.HourMAx,selected = The_Hour >= o.HourMin && The_Hour <= o.HourMAx}
;
query.OrderBy (q => q.HourMAx>The_Hour ? 0 : 1).ThenBy (q => q.HourMAx).Dump();
}
public class LS_CLIENTHORRAIRE
{
public string TheHour{get;set;}
public int HourMin{get;set;}
public int HourMAx{get;set;}
}
Results

So, basically, you don't want to filter the list, you want to sort it, right?
First, you want to sort it by
whether the MaxHour is in the past
and then by
TheHour itself.
Example: Let's assume it is 10:00:
Client_ID TheHour HourMin HourMax MaxHourIsInThePast
53026 09:00 7 9 x
53026 12:00 10 12
53026 15:00 13 15
53026 18:00 16 19
Now you return a list that orders first by MaxHourIsInThePast (first those without x and then those with x) and then by TheHour.
Implementation is left as an exercise. Hint: You will need the LINQ order by keyword, and an expression similar to (o.HourMax < currentHour ? 2 : 1) will come in handy.

Let assume the computer hour is 10.
Then: your condition would be: HourMin <= 10 && HoureMax >= 10.
The first condition would return row 1 and 2. The second one would return row 2. The intersect will return only the second row, which is 12:00.
If you want to get all rows, just remove these conditions.

C# LINQ query to use previous result if empty

I am having a datatable that is populated from an Access DB. The result looks like
Month | Sum
--------------
1 | 1464
2 | 1716
3 | 2125
4 | 2271
5 | 2451
6 | 2583
7 | 2671
9 | 2823
10 | 2975
You are right - nothing for august!
What I want is, that for august the same value as for july is used.
Currently I am using this LINQ query to add the data to a linechart:
for (int i = 1; i <= System.DateTime.Now.Month; i++)
{
var numbers = (from p in dTable.AsEnumerable()
where p.Field<int>("M") >= i
select p).First();
series2.Points.Add(new DataPoint { AxisLabel = i.ToString(), YValues = new double[] { Convert.ToDouble(numbers["Sum"]) } });
}
The chart is shown, but for august the september value is used. I assume it is something very basic that I am doing wrong but I simply can´t figure it out.
Thanks in advance!

You are requesting all the months greater than the current month.
where p.Field<int>("M") >= i
So for August (8), your are retrieving September and greater (9, 10, 11, 12), not July (7).
You have to invert your constraint, and order by descending month:
var numbers = (from p in dTable.AsEnumerable()
where p.Field<int>("M") <= i
select p)
.OrderByDesc(p => p.Month)
.First();

You have to invert your logic:
var numbers = (from p in dTable.AsEnumerable()
where p.Field<int>("M") <= i
select p).Last();
It goes without saying that this doesn't work when there is no previous month.
UPDATE:
the above asumes that the table you are reading from is ordered. If that is not the case, you have to order yourself (as mentioned by Cyril Gandon):
var numbers = (from p in dTable.AsEnumerable()
where p.Field<int>("M") <= i
orderby p.Field<int>("M") descending
select p).First();

LINQ Query to get values from database at specified time intervals

I want to fetch values from database with specific intervals in C# and need a LINQ query for that.
This is what my database looks like
Id SensorId Value CreatedOn
1 8 33.5 15-11-2012 5:48 PM
2 5 49.2 15-11-2012 5:48 PM
3 8 33.2 15-11-2012 5:49 PM
4 5 48.5 15-11-2012 5:49 PM
5 8 31.8 15-11-2012 5:50 PM
6 5 42.5 15-11-2012 5:50 PM
7 8 36.5 15-11-2012 5:51 PM
8 5 46.5 15-11-2012 5:51 PM
9 8 39.2 15-11-2012 5:52 PM
10 5 44.4 15-11-2012 5:52 PM
11 8 36.5 15-11-2012 5:53 PM
12 5 46.5 15-11-2012 5:53 PM
13 8 39.2 15-11-2012 5:54 PM
14 5 44.4 15-11-2012 5:54 PM
.. . .... ...................
The interval is in minutes.
So, if the interval is 10 minutes, then we need the values at 5:48, 5:58, 6:08 and so on...
This is what I have tried
while (startDateTime <= endDateTime)
{
var fetchIndex =
fullValues.Where(
item =>
item.CreatedOn >= startDateTime &&
item.CreatedOn < startDateTime.AddMinutes(1)).Select(
item => item.FetchIndex).FirstOrDefault();
if (fetchIndex != 0)
{
var temp = fullValues.Where(item => item.FetchIndex == fetchIndex).ToList();
result = result.Union(temp);
}
startDateTime = startDateTime.AddMinutes(interval);
}
Since the while loop iterates through the table, it takes a lot of time to get these values.
Is there any way of getting the data in a single query?

from x in table
where x.CreatedOn >= startDateTime &&
x.CreatedOn <= endDateTime &&
(x.CreatedOn.Minute % 10) == 0
select x
this will give you 1:00,1:10,1:20
The 10 represents your interval and 0 is your offset.

Following approach creates a list requiredTimes which holds all of the relevant datetimes between startDateTime and endDateTime (datetimes in 10 minute intervals between start and end datetimes).
After such list is created the fullValues is inner joined on it. The result is an IEnumerable with datetimes from fullValues that satisfy the interval condition. It should work fast since creating such list is quick and the Join method is an inner join which should also work fast, try it:
DateTime startDateTime = DateTime.Parse("15-11-2012 5:48 PM");
DateTime endDateTime = DateTime.Parse("16-11-2012 5:58 PM");
List<DateTime> requiredTimes = new List<DateTime>();
DateTime dt = startDateTime;
requiredTimes.Add(dt);
while (dt <= endDateTime)
{
dt = dt.AddMinutes(10);
requiredTimes.Add(dt);
}
var result = fullValues.Join(
requiredTimes,
fv => fv.CreatedOn,
rt => rt,
(fv, rt) => fv);

Group by Week of year (Week number) in Linq to SQL

In regular SQL i could do something like
SELECT * From T GROUP BY DATEPART(wk, T.Date)
How can i do that in Linq to SQL ?
The following don't work
From F In DB.T Group R By DatePart(DateInterval.WeekOfYear, F.Date)
Also don't work:
From F In DB.T Group R By (F.Date.DayOfYear / 7)

LINQ to SQL does not support the Calendar.WeekOfYear method, but you could potentially create a TSQL function that wraps the call to DatePart. The DayOfYear / 7 trick should work for most cases and is much easier to use. Here's the code I ended up with:
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()
};
Results in something like this:
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

You can use the SqlFunctions.DatePart method from the System.Data.Entity.SqlServer namespace.
// Return the week number
From F In DB.T Group R By SqlFunctions.DatePart("week", F.Date)

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

This works correctly.
from F in DB.T group F by F.Date.DayOfYear / 7;
You were specifying the group by incorrectly. The result of this code be a collection of objects. Each object will have a Key property which will be what you grouped by (in this case the result of F.Date.DayOfYear / 7. Each object will be a collection of objects from T that met the group condition.

If you are concerned about the culture you are in the following code will take that into account:
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;

First you should get the date of the first day in the week.
To get the date of the first day in the week.
you can use this code:
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;
}
}
Then you can group by the first date of the week.
So this code in regular SQL :
SELECT * From T GROUP BY DATEPART(wk, T.Date)
can be done in Linq to SQL like this
T.GroupBy(i => i.Date.StartOfWeek(DayOfWeek.Monday));