Simple line:
var x = (from a in arr select a).First();
Console.WriteLine(“First" + x);
How to convert to Lambda expression?
So you want to convert the LINQ query from using query syntax to plain extension method calls?
// var first = (from a in arr select a).First();
var first = arr.First();
// var last = (from a in arr select a).Last();
var last = arr.Last();
// var filtered = (from a in arr where a == 10 select a).First();
// there are a couple of ways to write this:
var filtered1 = arr.Where(a => a == 10)
.First();
var filtered2 = arr.First(a => a == 10); // produces the same result but obtained differently
// now a very complex query (leaving out the type details)
// var query = from a in arr1
// join b in arr2 on a.SomeValue equals b.AnotherValue
// group new { a.Name, Value = a.SomeValue, b.Date }
// by new { a.Name, a.Group } into g
// orderby g.Key.Name, g.Key.Group descending
// select new { g.Key.Name, Count = g.Count() };
var query = arr1.Join(arr2,
a => a.SomeValue,
b => b.AnotherValue,
(a, b) => new { a, b })
.GroupBy(x => new { x.a.Name, x.a.Group },
x => new { x.a.Name, Value = x.a.SomeValue, x.b.Date })
.OrderBy(g => g.Key.Name)
.ThenByDescending(g => g.Key.Group)
.Select(g => new { g.Key.Name, Count = g.Count() });
When you have an expression of the form (from y in x select y), you can almost always write x instead.
Related
Hi I am using below code to fetch required data from 2 tables using linq syntax which is working fine.
var ratings = from r in _ratingRepository.AsQueryable()
join c in _convRepository.AsQueryable()
on r.SessionId equals c.CurrentConversationSid
where!c.IsDeleted && c.DateCreated >= request.From && c.DateCreated <=
request.To && c.HasRated
select new Rating() {
Id = r.Id,
SessionId = r.SessionId,
Questions = r.Questions,
AvgRatingValue = r.AvgRatingValue
};
I want to transform this code using below syntax
IQueryable<Rating> ratingsObj = _ratingRepository.AsQueryable()
.Join(_convRepository.AsQueryable().Where(a => a.HasRated), r => r.SessionId, c => c.CurrentConversationSid, (r, c) =>
new Rating()
{
Id = r.Id,
SessionId = r.SessionId,
Questions = r.Questions,
AvgRatingValue = r.AvgRatingValue
});
Its gives below error
System.ArgumentException: 'Expression of type
'System.Collections.Generic.IEnumerable1[Flecx.Chat.Entities.Conversation]' cannot be used for parameter of type 'System.Linq.IQueryable1[Flecx.Chat.Entities.Conversation]' of method
'System.Linq.IQueryable1[Flecx.Chat.Entities.Conversation] Where[Conversation](System.Linq.IQueryable1[Flecx.Chat.Entities.Conversation],
System.Linq.Expressions.Expression1[System.Func2[Flecx.Chat.Entities.Conversation,System.Boolean]])'
(Parameter 'arg0')'
If I remove this code .Where(a => a.HasRated) it runs fine. How can I include the where clause in above syntax.
Need help
try this:
var ratingsObj = _ratingRepository.AsQueryable()
.Join(_convRepository.AsQueryable(),
r => r.SessionId,
c => c.CurrentConversationSid,
(r,c)=>new {r,c}) //**
.Where(a => a.c.HasRated)
.Select(x => new Rating()
{
Id = x.r.Id,
SessionId = x.r.SessionId,
Questions = x.r.Questions,
AvgRatingValue = x.r.AvgRatingValue
});
you can filter anything you want in line with '//**' same below:
(r, c) => new
{ r.Id,
r.SessionId,
r.Questions,
r.AvgRatingValue,
c.HasRated
}
then your code is changed to this:
var ratingsObj = _ratingRepository.AsQueryable()
.Join(_convRepository.AsQueryable(),
r => r.SessionId,
c => c.CurrentConversationSid,
(r, c) => new
{ r.Id,
r.SessionId,
r.Questions,
r.AvgRatingValue,
c.HasRated})
.Where(a => a.HasRated)
.Select(x => new Rating()
{
Id = x.Id,
SessionId = x.SessionId,
Questions = x.Questions,
AvgRatingValue = x.AvgRatingValue
});
I write query with method syntax where I use GroupBy than I can select list:
var q = foo.Join(ext, o => o.Id, i => i.fooId, (o, i) => new { tFirst = o, tSecond = i })
.GroupBy(p => p.tFirst, p => p.tSecond, (key, g) => new { tFirst = key, tSecondList = g.ToList() })
.Select(x => new
{
FooId = x.tFirst.Id, // I can select Id
Other = x.tFirst.Other, //and I can select other properties
Values = x.tSecondList.Select( ... ) // here I can select list
}
then I try to write this with query syntax but solution like this didn't worked:
var q = from f in foo
join e in ext on f.Id equals e.fooId
group new { e } by new { f, e.fooId } into g
How to write query syntax with group by so I finally can choose a list like in first snippet?
Something like this:
var q =
from f in foo
join e in ext on f.Id equals e.fooId
group e by new { f.Id, e.fooId } into g
select new
{
FooId = g.Key.Id,
Values = g.Select(x => ...).ToList()
}
I'm trying to convert my sql query to linq, i confused about sum and grouping,
this is my query
SELECT
produk.supplier,
SUM(transaksi.jumlah_transaksi),
SUM(transaksi.nominal_transaksi),
operasional.nominal
FROM
transaksi INNER JOIN produk ON transaksi.id_produk = produk.id_produk
LEFT JOIN
(SELECT
operasional.id_supplier,
SUM(nominal) AS nominal
FROM
operasional) operasional
ON operasional.id_supplier = produk.id_supplier
GROUP BY produk.supplier
output should be
like this
Progress
i am just trying with linq query like this without grouping
var result = from t in db.transaksi
join p in db.produk on t.id_produk equals p.id_produk
from op in
(
from o in db.operasional
select new
{
id_supplier = o.id_supplier,
nominal = o.nominal
}
).Where(o => o.id_supplier == p.id_supplier).DefaultIfEmpty()
select new
{
nama_supplier = p.supplier,
jumlah_transaksi = t.jumlah_transaksi,
nominal_transaksi = t.nominal_transaksi,
biaya_operasional = op.nominal
};
and result query from my linq still like this
SELECT
`p`.`supplier`,
`t`.`jumlah_transaksi`,
`t`.`nominal_transaksi`,
`t1`.`nominal`
FROM
`transaksi` `t`
INNER JOIN `produk` `p`
ON `t`.`id_produk` = `p`.`id_produk`
LEFT JOIN `operasional` `t1`
ON `t1`.`id_supplier` = `p`.`id_supplier`
Solved
and this is my full linq
var result = from t in db.transaksi
join p in db.produk on t.id_produk equals p.id_produk
from op in
(
from o in db.operasional
group o by o.id_supplier into g
select new
{
id_supplier = g.First().id_supplier,
nominal = g.Sum(o => o.nominal)
}
).Where(o => o.id_supplier == p.id_supplier).DefaultIfEmpty()
select new
{
nama_supplier = p.supplier,
jumlah_transaksi = t.jumlah_transaksi,
nominal_transaksi = t.nominal_transaksi,
biaya_operasional = op.nominal
};
var grouped = result
.GroupBy(x => x.nama_supplier)
.Select(x => new
{
nama_supplier = x.Key,
jumlah_transaksi = x.Sum(s => s.jumlah_transaksi),
nominal_transaksi = x.Sum(s => s.nominal_transaksi),
biaya_operasional = x.Select(s => s.biaya_operasional).First()
});
Try to use GroupBy (in following code result is your query from code above):
var grouped = result
.GroupBy(x => x.nama_supplier)
.Select(x => new {
nama_supplier = x.Key,
sum1 = x.Sum(s => s.jumlah_transaksi),
sum1 = x.Sum(s => s.nominal_transaksi),
nominal = x.Select(s => s.biaya_operasional).First()
})
Code is not checked so use it just as idea.
I would like to do a group by and on that a sum and a count. I don't seem to be able to create the solution in linq. How can I convert my query to linq?
SELECT HistoricalBillingProductGroup,
COUNT(*),
BillingPeriod,
SUM(TotalMonthlyChargesOtcAndMrc)
FROM [x].[dbo].[tblReport]
group by BillingPeriod, HistoricalBillingProductGroup
order by BillingPeriod
This is what I got sofar in Linq
var result =
context.Reports.GroupBy(x => new {x.BillingPeriod, x.HistoricalBillingProductGroup})
.Select(x => new StatisticsReportLine
{
HistoricalBillingGroup = x.FirstOrDefault().HistoricalBillingProductGroup,
BillingPeriod = x.FirstOrDefault().BillingPeriod,
CountOfRows = x.Count(),
SumOfAmount = x.Sum(p => p.TotalMonthlyChargesOtcAndMrc) ?? 0
})
.ToString();
The query I get from this is enormous and takes a very long time to load. In SQL its a matter of milliseconds. I hardly doubt this is the solution.
I believe the calls to x.FirstOrDefault() are the source of your problem. Each one of these will result in a very costly inner query inside the SELECT clause of the generated SQL.
Try using the Key property of the IGrouping<T> instead :
var result = context.Reports
.GroupBy(x => new {x.BillingPeriod, x.HistoricalBillingProductGroup})
.OrderBy(x => x.Key.BillingPeriod)
.Select(x => new StatisticsReportLine
{
HistoricalBillingProductGroup = x.Key.HistoricalBillingProductGroup,
BillingPeriod = x.Key.BillingPeriod,
CountOfRows = x.Count(),
SumOfAmount = x.Sum(p => p.TotalMonthlyChargesOtcAndMrc) ?? 0
});
Or if you prefer query syntax:
var result =
(from r in context.Reports
group r by new { r.BillingPeriod, r.HistoricalBillingProductGroup } into g
orderby g.Key.BillingPeriod
select new StatisticsReportLine
{
HistoricalBillingProductGroup = g.Key.HistoricalBillingProductGroup,
BillingPeriod = g.Key.BillingPeriod,
CountOfRows = g.Count(),
SumOfAmount = x.Sum(p => p.TotalMonthlyChargesOtcAndMrc) ?? 0
});
You could try this one:
var result = context.Reports
.GroupBy(x => new {x.BillingPeriod, x.HistoricalBillingProductGroup})
.Select(x => new StatisticsReportLine
{
HistoricalBillingGroup = x.Key.HistoricalBillingProductGroup,
BillingPeriod = x.Key.BillingPeriod,
CountOfRows = x.Count(),
SumOfAmount = x.Sum(p => p.TotalMonthlyChargesOtcAndMrc) ?? 0
}).ToString();
In the above query you make a group by on two properties, BillingPeriod and HistoricalBillingProductGroup. So in each group that will be created, you will have a key, that will be consisted by these two properties.
I am getting data from multiple tables by joining and i want to group data on particular column value but after group by statement i can access my aliases and their properties. What mistake i am making?
public List<PatientHistory> GetPatientHistory(long prid)
{
using(var db = new bc_limsEntities())
{
List<PatientHistory> result =
(from r in db.dc_tresult
join t in db.dc_tp_test on r.testid equals t.TestId into x
from t in x.DefaultIfEmpty()
join a in db.dc_tp_attributes on r.attributeid equals a.AttributeId into y
from a in y.DefaultIfEmpty()
where r.prid == prid
group new {r,t,a} by new {r.testid} into g
select new PatientHistory
{
resultid = r.resultid,
bookingid = r.bookingid,
testid = r.testid,
prid = r.prid,
attributeid = r.attributeid,
result = r.result,
Test_Name = t.Test_Name,
Attribute_Name = a.Attribute_Name,
enteredon = r.enteredon,
Attribute_Type = a.Attribute_Type
}).ToList();
return result;
}
}
You're doing this wrong way. As been said by Jon after grouping the sequences with aliases r,t,a doesn't exist. After grouping you receive the sequence g with sequances of r,t,a in each element of g. If you want get one object from each group (for example most recent) you should try this:
List<PatientHistory> result =
(from r in db.dc_tresult
join t in db.dc_tp_test on r.testid equals t.TestId into x
from t in x.DefaultIfEmpty()
join a in db.dc_tp_attributes on r.attributeid equals a.AttributeId into y
from a in y.DefaultIfEmpty()
where r.prid == prid
group new {r,t,a} by new {r.testid} into g
select new PatientHistory
{
resultid = g.Select(x => x.r.resultid).Last(), // if you expect single value get it with Single()
// .... here add the rest properties
Attribute_Type = g.Select(x => x.a.Attribute_Type).Last()
}).ToList();
I appreciated this question so I thought I would add another potential usage case. I would like feedback on what the cleanest approach is to getting table information through a group operation so that I can project later in the select operation. I ended up combining what the OP did which is to pass objects into his group clause and then used the g.Select approach suggested by YD1m to get table information out later. I have a LEFT JOIN so I'm defending against nulls :
// SQL Query
//DECLARE #idCamp as Integer = 1
//
//select *,
//(select
//count(idActivityMaster)
//FROM tbActivityMasters
//WHERE dftidActivityCategory = A.idActivityCategory) as masterCount
//FROM tbactivitycategories A
//WHERE idcamp = #idCamp
//ORDER BY CategoryName
int idCamp = 1;
var desiredResult =
(from c in tbActivityCategories
.Where(w => w.idCamp == idCamp)
from m in tbActivityMasters
.Where(m => m.dftidActivityCategory == c.idActivityCategory)
.DefaultIfEmpty() // LEFT OUTER JOIN
where c.idCamp == idCamp
group new {c, m} by new { m.dftidActivityCategory } into g
select new
{
idActivityCategory = g.Select(x => x.m == null ? 0 : x.m.dftidActivityCategory).First(),
idCamp = g.Select(x => x.c.idCamp).First(),
CategoryName = g.Select(x => x.c.CategoryName).First(),
CategoryDescription = g.Select(x => x.c.CategoryDescription).First(),
masterCount = g.Count(x => x.m != null)
}).OrderBy(o=> o.idActivityCategory);
desiredResult.Dump("desiredResult");
If I just use a basic group approach I get the results but not the extra column information. At least I can't find it once I group.
var simpleGroup = (from c in tbActivityCategories
.Where(w => w.idCamp == idCamp)
.OrderBy(o => o.CategoryName)
from m in tbActivityMasters
.Where(m => m.dftidActivityCategory == c.idActivityCategory)
.DefaultIfEmpty() // LEFT OUTER JOIN
where c.idCamp == idCamp
group m by m == null ? 0 : m.dftidActivityCategory into g
select new
{
// How do I best get the extra desired column information from other tables that I had before grouping
// but still have the benefit of the grouping?
// idActivityCategory = g.Select(x => x.m == null ? 0 : x.m.dftidActivityCategory).First(),
// idCamp = g.Select(x => x.c.idCamp).First(),
// CategoryName = g.Select(x => x.c.CategoryName).First(),
// CategoryDescription = g.Select(x => x.c.CategoryDescription).First(),
// masterCount = g.Count(x => x.m != null)
idActivityCategory = g.Key,
masterCount = g.Count(x => x != null)
});
simpleGroup.Dump("simpleGroup");
Please tear this up. I'm trying to learn and it just seems like I'm missing the big picture here. Thanks.
UPDATE : Cleaned up by moving the work into the group and making the select more straight forward. If I had known this yesterday then this would have been my original answer to the OP question.
int idCamp = 1;
var desiredResult =
(from c in tbActivityCategories
.Where(w => w.idCamp == idCamp)
from m in tbActivityMasters
.Where(m => m.dftidActivityCategory == c.idActivityCategory)
.DefaultIfEmpty() // LEFT OUTER JOIN
where c.idCamp == idCamp
group new { c, m } by new
{ idActivityCategory = m == null ? 0 : m.dftidActivityCategory,
idCamp = c.idCamp,
CateGoryName = c.CategoryName,
CategoryDescription = c.CategoryDescription
} into g
select new
{
idActivityCategory = g.Key.idActivityCategory,
idCamp = g.Key.idCamp,
CategoryName = g.Key.CateGoryName,
CategoryDescription = g.Key.CategoryDescription,
masterCount = g.Count(x => x.m != null)
}).OrderBy(o => o.idActivityCategory);
desiredResult.Dump("desiredResult");