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EF Core 2.1 group by with skip and take

I a currently "paging" through an IQueryable that has many fields { Table1Id, Table1Label, IsActive, ...} and there can be mulitple records in IQueryable result for a PdcId, like the following:
var result = from a in _entities.table1
join b in _entities.table2 on new { a.Table1Id, a.Table1LevelId } equals new { Table1Id = b.Table2Id, Table1LevelId = b.Table2LevelId }
join c in _entities.Table3 on a.Table1Id equals c.Table1Id into cc from ccc in cc.DefaultIfEmpty()
where a.Valide == true
select new MeteringPointDetailModel
{
Table1Id = a.Table1Id,
Table1Label = a.Label,
IsActive = a.IsActive,
Table3Label = ccc.Label,
};
I tried this code but when i see the result generating in sql using sql profiler, the query is running without stop !! (generate multiple sql query ).
var data = await result.Where(i => result.GroupBy(p => p.Table1Id)
.Select(t => t.Key)
.Skip(query.Page).Take(query.PageSize)
.Contains(i.Table1Id)).ToListAsync();
How would I do this if I wanted to first group by Table1Id and then skip and take on the distinct Table1Id.
for example: if I have a result that has two records, one ends up being # 50 and the other 51, if I page by 50, I won't get record 51, and I want it.

That's what i did and worked for me :
Solution 1
var dataTable1 = (from a in _entities.table1
where a.Valide == true
select new {...}).Skip(query.Page).Take(query.PageSize);
var result = from a in dataTable1
join b in _entities.table2 on new { a.Table1Id, a.Table1LevelId } equals new { Table1Id = b.Table2Id, Table1LevelId = b.Table2LevelId }
join c in _entities.Table3 on a.Table1Id equals c.Table1Id into cc from ccc in cc.DefaultIfEmpty()
select new MeteringPointDetailModel
{
Table1Id = a.Table1Id,
Table1Label = a.Label,
IsActive = a.IsActive,
Table3Label = ccc.Label,
};
var data = await result.ToListAsync();
Solution 2
var result = from a in _entities.table1
join b in _entities.table2 on new { a.Table1Id, a.Table1LevelId } equals new { Table1Id = b.Table2Id, Table1LevelId = b.Table2LevelId }
join c in _entities.Table3 on a.Table1Id equals c.Table1Id into cc from ccc in cc.DefaultIfEmpty()
where a.Valide == true
select new MeteringPointDetailModel
{
Table1Id = a.Table1Id,
Table1Label = a.Label,
IsActive = a.IsActive,
Table3Label = ccc.Label,
};
result = !string.IsNullOrWhiteSpace(query.Table3Label) ? result.Where(c => c.Table3Label.ToLower().Contains(query.Table3Label.ToLower())) : result;
var table1Ids = await result.OrderBy(p => p.Table1Id)
.Select(p => p.Table1Id).Distinct()
.Skip(query.Page).Take(query.PageSize)
.ToListAsync();
var data = await result.Where(p => table1Ids.Contains(p.Table1Id)).ToListAsync();
Solution 2 is more useful if there are clause condition (search criteria) in join tables as specified in the example.
Hope it will help someone.

Calculating product's quantity with nested EF Query

I want to calculate the quantity of every product. I want to use these tables for this.
I want take result like this.
StockId | StockName | Sum(ProductNumber) [actually product quantity]
I tried this code for can take right result but It is returning null value even though it is the condition that satisfies the conditions.
CimriContext context = new CimriContext();
public ICollection<StockDto.StockHeader> FillDataGrid(int userCompanyId)
{
ICollection<StockDto.StockHeader> Stocks = context.Stocks.Where(c => c.UserCompanyId==userCompanyId).
Select(c => new StockDto.StockHeader()
{
StockId = c.StockId,
StockName = c.StockName,
Piece=0
}).ToList();
ICollection<StockDto.StockHeader> ProductHeader = new List<StockDto.StockHeader>();
foreach (var products in Stocks)
{
products.Piece = context.ProductTransactions.Where(p => p.StockId==products.StockId).Sum(s => s.ProductNumber);
ProductHeader.Add(products);
}
return ProductHeader.ToList();
}

You want to retrieve ProductCount for per stock record. You can perform it by joining two tables and grouping StockId and StockNumber like this;
var query = from stocks in context.Stocks
join products in context.ProductTransactions ON stocks.StockId equals products.StockId
where stocks.UserCompanyId = userCompanyId
group stocks by new
{
stocks.StockId,
stocks.StockName
} into gcs
select new
{
StockId = gcs.Key.StockId,
StockName = gcs.Key.StockName,
ProductCounts = gcs.Count()
};

Sum(with Coalesce) with Group By in linq (for EF6)

I have the following SQL that I would like to write as a single linq statement:
SELECT
P.PartyId,
P.PartyDate,
SUM(COALESCE(R.PaidAmount, 0)) AS AmountPaid
FROM
Party AS P
LEFT JOIN Reservation as R
ON P.PartyID = R.PartyID
GROUP BY P.PartyID, P.PartyDate
ORDER BY P.PartyDate DESC
The best I can do is use two sets of linq queries, like so:
var localList = from partyList in localDb.Parties
join reservationList in localDb.Reservations on
partyList.PartyID equals reservationList.PartyID into comboList
from newList in comboList.DefaultIfEmpty()
select new PartyAmounts {
PartyID = partyList.PartyID,
PartyDate = partyList.PartyDate,
AmountPaid = (newList.PaidAmount ?? 0) };
var secondList = from groupList in localList
group groupList by new {
groupList.PartyID,
groupList.PartyDate} into resList
select new PartyAmounts {
PartyID = resList.Key.PartyID,
PartyDate=resList.Key.PartyDate,
AmountPaid = resList.Sum(x => x.AmountPaid)};
I don't care if it's a method chain or a lambda but I would love to know how this is supposed to go together. I can only barely understand the two I've got now.
Thanks for the help.

var list = from partyList in localDb.Parties
join reservationList in localDb.Reservations on partyList.PartyID equals reservationList.PartyID into comboList
from details in comboList.DefaultIfEmpty() // Left join
group details by new {partyList.PartyID, partyList.PartyDate} into grouped // So that the group have both keys and all items in details
select new PartyAmounts
{
PartyID = grouped.Key.PartyID,
PartyDate = grouped.Key.PartyDate,
AmountPaid = grouped.Sum(x => x.AmountPaid ?? 0)}
};

SQL to Linq select multiple columns in group by

I would like to convert a SQL statement to LINQ but i have some problems doing it.
The sql statement is :
SELECT
C.[Call_Date], CC.[Company], R.Resolution,
COUNT_BIG(*) AS CNT,
SUM([Duration]) AS Total
FROM
[Calls] C
Join
[CompanyCharges] CC on [Company_Charge] = [CompanyCharge]
Join
[Resolutions] R on C.Call_Resolution = R.Resolution
where
Call_Date >= '05/29/2013'
Group By
C.[Call_Date], CC.[Company], CC.[CompanyCharge], R.Resolution, R.Resolution_Order
I wrote something like :
var stats = from c in dbContext.Calls
join cc in dbContext.CompanyCharges on c.Company_Charge equals cc.CompanyCharge
join r in dbContext.Resolutions on c.Call_Resolution equals r.Resolution
where (c.Call_Date > "05/29/2013")
group new { c, cc, r } by new { c.Call_Date, cc.CompanyCharge, r.Resolution, r.Resolution_Order } into statsGroup
select new { Count = statsGroup.Count(), ??? };
I managed to count the elements, but i need a sum[duration] and some columns from different tables.
Please share your wisdome with me.

Assuming that the [Duration] field is part of the [Calls] table:
var stats = /* ... */
select new
{
Count = statsGroup.Count(),
Total = statsGroup.Sum(stat => stat.c.Duration),
};
You'd probably want to include your grouping fields in the new anonymous type as well:
var stats = /* ... */
select new
{
Call_Date = statsGroup.Key.c.Call_Date,
CompanyCharge = statsGroup.Key.cc.CompanyCharge,
Resolution = statsGroup.Key.r.Resolution,
Count = statsGroup.Count(),
Total = statsGroup.Sum(stat => stat.c.Duration),
};

Linq to SQL in C# Unique data

I have a long list with ships that I get from a Linq to SQL query, but I only want one row per ImoNo. Today i have about 4 rows per ImoNo. I just need the one row that has been last updated (so in this example I need 2013-01-27).
This is my Linq To SQL query:
var res = from positions in context.Lloyds_ETAs
join vessels in context.Lloyds_Vessels on positions.ImoNumber equals vessels.imo_no
select new PositionData {
ImoNo = positions.ImoNumber,
PositionCordinates = positions.AIS_Latest_Position,
CompassOverGround = positions.Compass_over_Ground_Heading,
VesselId = positions.Vessel_ID,
Equipment = vessels.vessel_type,
Updated = positions.Last_Place_Location
};
return res.ToList();

var res = (from positions in context.Lloyds_ETAs
join vessels in context.Lloyds_Vessels on positions.ImoNumber equals vessels.imo_no
select new PositionData {
ImoNo = positions.ImoNumber,
PositionCordinates = positions.AIS_Latest_Position,
CompassOverGround = positions.Compass_over_Ground_Heading,
VesselId = positions.Vessel_ID,
Equipment = vessels.vessel_type,
Updated = positions.Last_Place_Location
})
.GroupBy(x => x.ImoNo)
.Select(g => g.OrderByDescending(pd => pd.Updated).First());

If you want the last one, all you have to do is append .OrderBy(pd => pd.Updated).Last() after your select.
var res = (from positions in context.Lloyds_ETAs
join vessels in context.Lloyds_Vessels on positions.ImoNumber equals vessels.imo_no
select new PositionData {
ImoNo = positions.ImoNumber,
PositionCordinates = positions.AIS_Latest_Position,
CompassOverGround = positions.Compass_over_Ground_Heading,
VesselId = positions.Vessel_ID,
Equipment = vessels.vessel_type,
Updated = positions.Last_Place_Location
}).OrderBy(pd => pd.Updated).Last();
return res.ToList();

(yourQuery).OrderByDescending(pd=>pd.Updated).First()

There are several ways to get just one "row" as a result:
res.OrderByDescending(x => x.Updated).Take(1);
res.OrderByDescending(x => x.Updated).First();
res.Order(x => x.Updated).Last();
It seems that you have some duplication though, so maybe doing a group by would be more appropriate.