Develop Reference

LINQ 3 Inner Joins with 1 Left Outer Join

Wondering why LINQ doesn't have a Left Join method. I've been trying to figure this out with myriad examples on SO, but no such luck. The other examples show simple examples with one join. If I group the joins then I only get references to the TradeCountries table in the select statement.
Being new to LINQ, I could've had this done 4 hours ago with a simple SELECT statement, but here I'm am trying to figure out why the LeftJoin method was left out of LINQ.
What does the line with "LeftJoin" need to be changed to make this work?
/*
* GetTop5Distributors
#param int array of series IDs
*/
public List<TopDistributors> Get5TopDistributors(IEnumerable<int> seriesIds)
{
_context = new MySQLDatabaseContext();
var result = _context.TradesTrades
.Join(_context.TradesSeries, tt => tt.SeriesId, ts => ts.Id, (tt, ts) => new { tt, ts })
.Join(_context.TradesTradeDistributors, tsd => tsd.tt.Id, ttd => ttd.TradeId,
(tsd, ttd) => new { tsd, ttd })
.Join(_context.TradesOrganisations, tsdto => tsdto.ttd.DistributorId, to => to.Id,
(tsdto, to) => new { tsdto, to })
.LeftJoin(_context.TradesCountries, tsdc => tsdc.to.CountryId, tc => tc.Id,
(tsdc, tc) => new {tsdc, tc})
.Where(x => seriesIds.Contains(x.tsdc.tsdto.tsd.tt.SeriesId))
.Where(x => x.tsdc.tsdto.tsd.tt.FirstPartyId == null)
.Where(x => x.tsdc.tsdto.tsd.tt.Status != "closed")
.Where(x => x.tsdc.tsdto.tsd.tt.Status != "cancelled")
.GroupBy(n => new { n.tsdc.tsdto.tsd.tt.SeriesId, n.tsdc.tsdto.ttd.DistributorId })
.Select(g =>
new TopDistributors
{
SeriesId = g.Key.SeriesId,
DistributorName = g.Select(i => i.tsdc.to.Name).Distinct().First(),
IsinNickname = g.Select(i => i.tsdc.tsdto.tsd.ts.Nickname).Distinct().First(),
CountryName = g.Select(i => i.tc.Name).Distinct().First(),
CommissionTotal = Math.Ceiling(g.Sum(i => i.tsdc.tsdto.ttd.Commission))
}
)
.OrderByDescending(x => x.CommissionTotal)
.Take(5)
.ToList();
return result;
}
Here's the rather simple select statement that is taking orders or magnitude too long to convert to LINQ.
SELECT
trades_trades.series_id,
trades_organisations.`name`,
trades_series.nickname,
trades_countries.name as Country_Name,
SUM(trades_trade_distributors.commission) as Commission_Total
FROM
trades_trades
JOIN trades_series
ON trades_series.id = trades_trades.series_id
JOIN trades_trade_distributors
ON trades_trades.id = trades_trade_distributors.trade_id
JOIN trades_organisations
ON trades_trade_distributors.distributor_id = trades_organisations.id
LEFT JOIN trades_countries
ON trades_organisations.country_id = trades_countries.id
WHERE trades_trades.series_id IN (
17,
18)
AND trades_trades.first_party_id IS NULL
AND trades_trades.status <> 'closed'
AND trades_trades.status <> 'cancelled'
GROUP BY trades_trades.series_id, trades_trade_distributors.distributor_id
ORDER BY Commission_Total DESC

Following my recipe, here is a more or less straightforward translation of the SQL to LINQ. I moved the where to be near what it constrains, and used let to create a convenient name for the Sum, as LINQ doesn't allow you to forward reference anonymous object members.
var ans = from tt in trades_trades
where new[] { 17, 18 }.Contains(tt.series_id) && tt.first_party_id == null &&
tt.status != "closed" && tt.status != "cancelled"
join ts in trades_series on tt.series_id equals ts.id
join ttd in trades_trade_distributors on tt.id equals ttd.trade_id
join to in trades_orginizations on ttd.distributor_id equals to.id
join tc in trades_countries on to.country_id equals tc.id into tcj
from tc in tcj.DefaultIfEmpty() // GroupJoin -> left join
group new { tt, ts, ttd, to, tc } by new { tt.series_id, ttd.distributor_id } into tradeg
let Commission_Total = tradeg.Sum(trade => trade.ttd.commission)
orderby Commission_Total descending
select new {
tradeg.Key.series_id,
tradeg.First().to.name,
tradeg.First().ts.nickname,
Country_Name = tradeg.First().tc == null ? null : tradeg.First().tc.name,
Commission_Total
};

How to get record with max date with join?

How can I do this in LINQ?
select MAX(d.DepartureDateRange),MAX(d.ReturnDateRange)
from Tour t join
TourCategory tc on t.ID = tc.TourID
join TourDates td on t.ID = td.TourID
join Dates d on d.ID = td.DatesID
where tc.CategoryID = 3 and t.ID = 12
Database diagram is here ->
For example joins is like this but i cannot get Max of DepartureDateRange & ReturnDateRange
var query2 = from t in db.Tour
join tc in db.TourCategory on t.ID equals tc.TourID
join td in db.TourDates on t.ID equals td.TourID
join d in db.Dates on td.DatesID equals d.ID
where tc.CategoryID == 3
select new IndexTour
{
ID = t.ID,
TourName = t.TourName,
//DepartureDateRange =
//ReturnDateRange =
Description = t.SmallDesc,
Price = t.Price,
CoverPhotoUrl = t.CoverPhotoUrl,
TourProgram = t.TourDesc
};
Thanks in advance.

Here it is (dates are grouped by Tour):
var query2 =
from t in db.Tour
join tc in db.TourCategory on t.ID equals tc.TourID
where tc.CategoryID == 3
// join dates aggregates grouped by tour id
join tdates in
from td in db.TourDates
join d in db.Dates on td.DatesID equals d.ID
group d by td.TourID into grp
select new
{
tourID = grp.Key,
departure = grp.Max(g => g.DepartureDateRange),
rtrn = grp.Max(g => g.ReturnDateRange)
}
on t.ID equals tdates.tourID
select new IndexTour
{
ID = t.ID,
TourName = t.TourName,
DepartureDateRange = tdates.departure,
ReturnDateRange = tdates.rtrn,
Description = t.SmallDesc,
Price = t.Price,
CoverPhotoUrl = t.CoverPhotoUrl,
TourProgram = t.TourDesc
};

I think this is what you want?
var dateRanges = tours
.Join(tourCategories,
t => t.Id,
tc => tc.TourId,
(t, tc) => (t, tc))
.Join(tourDates,
ttc => ttc.t.Id,
td => td.TourId,
(ttc, td) => (ttc, td))
.Join(dates,
ttctd => ttctd.td.DateId,
d => d.Id,
(ttctd, d) =>
new {
TourId = ttctd.ttc.t.Id,
CategoryId = ttctd.ttc.tc.CategoryId,
DepartureDateRange = d.DepartureDateRange,
ReturnDateRange = d.ReturnDateRange
});
var filtered = dateRanges
.Where(r => r.CategoryId == 3 && r.TourId == 12);
var maxDepartureDateRange = filtered.Max(d => d.DepartureDateRange);
var maxReturnDateRange = filtered.Max(d => d.ReturnDateRange);

Error in Linq query when join multiple table

My linq query is:
var query1 = (from grp in ctnx.tblGroupDatas
group grp by grp.MeterID_FK into g
let maxId = g.Max(gId => gId.GroupDataID)
select new { metId = g.Key, maxId });
query2 = (from met in ctnx.tblMet
from mod in ctnx.tblMod.Where(mo => mo.ModID == met.Mod_FK).DefaultIfEmpty()
from grp in ctnx.tblGroupDatas.Where(gr => gr.Met_FK == met.MetID)
from group1 in db.tblMetRelateGroups.Where(x => x.Met_FK == met.MetID)
from q1 in query1.Where(q => q.metId == met.MetID && grp.GroupDataID == q.maxId)
where (group1.GroupMetID_FK == groupID)
select new
{
met.MetID,
mod.ModSerial,
met.MetSerial,
met.MetWaterSharingNo,
met.MetPowerSharingNo,
grp.GroupDate,
grp.GroupDataID
});
var gridobisdata = query2.OrderByDescending(m => m.GroupDate);
but this show error:
The specified LINQ expression contains references to queries that are
associated with different contexts.

How to Select new model list after GroupBy mothod in Linq?

I want select grouped rows to a new model list.this is my code:
List<Model_Bulk> q = (from a in db.Advertises
join c in db.Companies on a.AdvertiseCompanyID equals c.CompanyID
where a.AdvertiseActive == true
&& a.AdvertiseExpireDate.HasValue
&& a.AdvertiseExpireDate.Value > DateTime.Now
&& (a.AdvertiseObjectType == 1
|| a.AdvertiseObjectType == 2)
select c)
.GroupBy(a => a.CompanyID).Select(a => new Model_Bulk
{
CompanyEmail = a.CompanyContactInfo.Email,
CompanyID = a.CompanyID,
CompanyName = a.CompanyName,
Mobile = a.CompanyContactInfo.Cell,
UserEmail = a.User1.Email,
categories = a.ComapnyCategories
}).ToList();
After group by, i can not use Select and naturally this syntax error raised:
System.Linq.IGrouping' does not contain a definition for 'CompanyContactInfo' and no extension method 'CompanyContactInfo' accepting a first argument of type
System.Linq.IGrouping' could be found (are you missing a using directive or an assembly reference?)
If i try with SelectMany() method.but the result will repeated and groupby method not work properly:
List<Model_Bulk> q = (from a in db.Advertises
join c in db.Companies on a.AdvertiseCompanyID equals c.CompanyID
where a.AdvertiseActive == true
&& a.AdvertiseExpireDate.HasValue
&& a.AdvertiseExpireDate.Value > DateTime.Now
&& (a.AdvertiseObjectType == 1
|| a.AdvertiseObjectType == 2)
select c)
.GroupBy(a => a.CompanyID).SelectMany(a => a).Select(a => new Model_Bulk
{
CompanyEmail = a.CompanyContactInfo.Email,
CompanyID = a.CompanyID,
CompanyName = a.CompanyName,
Mobile = a.CompanyContactInfo.Cell,
UserEmail = a.User1.Email,
categories = a.ComapnyCategories
}).ToList();

Instead of .SelectMany(a => a) you can use .Select(g => g.First()).That will give you the first item of each group.
(from a in db.Advertises
join c in db.Companies on a.AdvertiseCompanyID equals c.CompanyID
where a.AdvertiseActive == true && a.AdvertiseExpireDate.HasValue && a.AdvertiseExpireDate.Value > DateTime.Now && (a.AdvertiseObjectType == 1 || a.AdvertiseObjectType == 2)
select c)
.GroupBy(a => a.CompanyID)
.Select(g => g.First())
.Select(a => new Model_Bulk
{
CompanyEmail = a.CompanyContactInfo.Email,
CompanyID = a.CompanyID,
CompanyName = a.CompanyName,
Mobile = a.CompanyContactInfo.Cell,
UserEmail = a.User1.Email,
categories = a.ComapnyCategories
}).ToList();
Note that this might not be supported, if that is the case add an AsEnumerable call before .Select(g => g.First())

You should understand that after you do GroupBy() in your LinQ expresstion you work with a group so in your example it will be good to write like this:
List<Model_Bulk> q =
(from a in db.Advertises join c in db.Companies on a.AdvertiseCompanyID equals c.CompanyID
where a.AdvertiseActive == true
&& a.AdvertiseExpireDate.HasValue
&& a.AdvertiseExpireDate.Value > DateTime.Now
&& (a.AdvertiseObjectType == 1 || a.AdvertiseObjectType == 2)
select c)
.GroupBy(a => a.CompanyID)
.Select(a => new Model_Bulk
{
CompanyEmail = a.First().CompanyContactInfo.Email,
CompanyID = a.Key, //Note this line, it's can be happened becouse of GroupBy()
CompanyName = a.First().CompanyName,
Mobile = a.First().CompanyContactInfo.Cell,
UserEmail = a.First().User1.Email,
categories = a.First().ComapnyCategories
}).ToList();

Instead you could try something like this, instead of mixing query expressions and methods... (using FirstOrDefault() in the where / select as necessary)
(from a in db.Advertises
join c in db.Companies on a.AdvertiseCompanyID equals c.CompanyID
group a by new { a.CompanyId } into resultsSet
where resultsSet.AdvertiseActive == true && resultsSet.AdvertiseExpireDate.HasValue && resultsSet.AdvertiseExpireDate.Value > DateTime.Now && (resultsSet.AdvertiseObjectType == 1 || resultsSet.AdvertiseObjectType == 2)
select new Model_Bulk
{
CompanyEmail = resultsSet.CompanyContactInfo.Email,
CompanyID = resultsSet.CompanyID,
CompanyName = resultsSet.CompanyName,
Mobile = resultsSet.CompanyContactInfo.Cell,
UserEmail = resultsSet.User1.Email,
categories = resultsSet.ComapnyCategories
}).ToList();

Entity Framework with Linq, inner Join, Group By, Order By

I have a SQL Query
select Firma.Name as companyName,
Taetigkeit.Taetigkeit as skillName,
SUM(Zeit) as time
from Zeiterfassung
inner join Firma On ZEiterfassung.FirmenID = Firma.ID
inner join Taetigkeit on Zeiterfassung.TaetigkeitID = Taetigkeit.ID
group by Taetigkeit, Firma.Name
order by Firma.Name
And want to "translate" it to linq. Here is what I tried:
var query = db.Zeiterfassung
.Where(x => x.Firma.ID == x.FirmenID && x.TaetigkeitID == x.Taetigkeit.ID)
.GroupBy(x => x.Taetigkeit.Taetigkeit1)
.Select(x => new Evaluation() { skillName = x.Key, time = x.Sum(y => y.Zeit), //skillName = x.Sum(x => x.Zeit), })
.OrderBy(x => x.skillName);
I dont know who to solve this with joins and the group by because all the time when i do a groupBy i cant access the other members.

From data you provided, I think query should look like
from z in db.Zeiterfassung
join f in db.Firma on z.FirmenID equals f.ID
join t in db.Taetigkeit on z.TaetigkeitID equals t.ID
select new { f.Name, t.Taetigkeit, z.Zeit) into x
group x by new { x.Taetigkeit, f.Name } into g
select new {
CompanyName = g.Key.Name,
SkillName = g.Key.Taetigkeit,
Time = g.Sum(i => i.Zeit)
}
Or with navigation properties:
db.Zeiterfassung
.Select(z => new { z.Zeit, z.Taetigkeit.Taetigkeit1, z.Firma.Name })
.GroupBy(x => new { x.Taetigkeit1, x.Name })
.Select(g => new Evaluation {
companyName = g.Key.Name,
skillName = g.Key.Taetigkeit1,
time = g.Sum(y => y.Zeit)
});