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Multiple Left Join with Linq and Defaults Values

I'm trying to write a query that contains multiple left joins in linq in a c# .netcore 2.2 application. I've tried writing the query in linq but it is not properly retrieving all the rows. Query I'm trying to convert is as follows.
select ISNULL(b.Id, '00000000-0000-0000-0000-000000000000') as 'Bat Id', p.Id as 'ProductId', p.RP, u.UnitName as 'UnitName', ISNULL(b.QTY,0) as 'BusQty', p.[Name] as 'Product Name'
from Products p left join Bat b
ON p.Id = b.ProductId
left join Units u on p.UOId = u.Id;
linq I have so far
var allProducts = (from p in _db.Products
join s in _db.Bat on p.Id equals s.ProductId into ps
from s in ps.DefaultIfEmpty()
join u in _db.Units on p.UOId equals u.Id
select new
{
BatId = s.Id == null ? Guid.NewGuid() : s.Id,
RP = p.RP,
BusQty = s.QTY == null ? 0 : s.QTY,
ProductName = p.Name,
UnitName = u.UnitName,
ProductId = p.Id,
}).ToList();

You are missing DefaultIfEmpty() on Units, thereby turning it into an inner join
var allProducts = (
from p in _db.Products
join s in _db.Bat on p.Id equals s.ProductId into ps
from s in ps.DefaultIfEmpty()
join u in _db.Units on p.UOId equals u.Id into us
from u in us.DefaultIfEmpty()
select new
{
BatId = s.Id ?? Guid.NewGuid(),
RP = p.RP,
BusQty = s.QTY ?? 0,
ProductName = p.Name,
UnitName = u.UnitName,
ProductId = p.Id,
}).ToList();

Convert SqlServer Query to LINQ

I have written the below given query in SQL server 2008:
(SELECT p.postid,
p.title,
p.disabled,
l.locationname
FROM posts p
INNER JOIN categories c
ON p.categoryid = c.categoryid
INNER JOIN users u
ON p.userid = u.userid
INNER JOIN tags t
ON p.tagid = t.tagid
INNER JOIN locations l
ON p.locationid = l.locationid
LEFT JOIN postimages pm
ON p.postid = pm.postid
WHERE p.categoryid = 1
GROUP BY p.postid,
p.title,
p.disabled,
l.locationname)
ORDER BY p.postid DESC
I want to write the above query in LINQ.
I tried a little and able to write the query below:
var objPosts = (from p in _dbcontext.Posts
join us in _dbcontext.Users on p.UserId equals us.UserId
join tag in _dbcontext.Tags on p.TagId equals tag.TagId
join cat in _dbcontext.Categories on p.CategoryId equals cat.CategoryId
join loc in _dbcontext.Locations on p.LocationId equals loc.LocationId
join img in _dbcontext.PostImages on p.PostId equals img.PostId into gj
from postimg in gj.DefaultIfEmpty()
where p.Disabled == false && p.CategoryId == userPost.CategoryId || p.UserId == userPost.UserId || p.TagId == userPost.TagId || p.LocationId == userPost.LocationId
orderby p.PostId descending
select new
{
PostId = p.PostId,
PostTitle = p.Title,
//ImageInfo = postimg.ImagePath,
//ThumbNailInfo = p.ThubNailInfo,
PostShortDescription = p.ShortDescription,
UserId = us.UserId,
UserName = us.Name,
TagId = tag.TagId,
TagTitle = tag.Title,
CategoryId = cat.CategoryId,
CategoryName = cat.CategoryName,
LocationId = loc.LocationId,
LocationName = loc.LocationName
});
I am unable to apply the group by logic in LINQ. Can anyone please convert my SQL to LINQ. Thanks

group new { p, l } by new
{
p.postid,
p.title,
p.disabled,
l.locationname
} into g
orderby g.Key.PostId descending
select new
{
g.key.postid,
g.key.title,
g.key.disabled,
g.key.locationname
}

The missing part in your query is that you are not selecting anything...
You got the joins ok, left outer join ok, predicates (where), ordering, but no projection, and no group by.
Below should get you started:
group p by p.PostId into pg
select new {Post=p, Location=loc};
This would return return a collection of new objects whose properties Post and Location.

How to Join LINQ to another LINQ

i have a query like this
WITH CTE_KELOMPOKINFORMASI (KelompokInformasi, XBRLItem_ItemId)
AS (
SELECT a.Id AS KelompokInformasi, c.XBRLItem_ItemId
FROM XBRLNamespaces a INNER JOIN XBRLHypercubes b
ON a.XBRLView_ViewId = b.XBRLView_ViewId
INNER JOIN XBRLHypercubeDimensionItems c
ON b.XBRLHypercubeId = c.XBRLHypercube_XBRLHypercubeId
WHERE a.Id like '%KBIK_AAKL%')
SELECT f.KelompokInformasi, e.Name AS DimensionName, c.Id AS Domain,
d.Text AS Description FROM [dbo].[XBRLDefinitionRoleDomainItems] a
INNER JOIN [dbo].[XBRLDefinitionRoleDimensionItems] b
ON a.XBRLDefinitionRole_DefinitionRoleId = b.XBRLDefinitionRole_DefinitionRoleId
INNER JOIN XBRLItems c ON a.XBRLItem_ItemId = c.ItemId
INNER JOIN XBRLLabels d
ON a.XBRLItem_ItemId = d.XBRLItem_ItemId
INNER JOIN XBRLItems e
ON b.XBRLItem_ItemId=e.ItemId
INNER JOIN CTE_KELOMPOKINFORMASI f
ON b.XBRLItem_ItemId=f.XBRLItem_ItemId
WHERE b.XBRLItem_ItemId=f.XBRLItem_ItemId
i want to move this sql query to linq, i realized that CTE is impossible in LINQ. So i divide into 2 parts. First i create a var like this:
var KelompokInformasi = from x in ent.XBRLNamespaces
join y in ent.XBRLHypercubes on x.XBRLView_ViewId equals y.XBRLView_ViewId
join z in ent.XBRLHypercubeDimensionItems on y.XBRLHypercubeId equals z.XBRLHypercube_XBRLHypercubeId
where x.Id.Contains("KBIK")
select new
{
x.Id,
y.XBRLItem_ItemId
};
and in second part i create:
_list = (from a in ent.XBRLDefinitionRoleDomainItems
join b in ent.XBRLDefinitionRoleDimensionItems on a.XBRLDefinitionRole_DefinitionRoleId equals b.XBRLDefinitionRole_DefinitionRoleId
join c in ent.XBRLItems on a.XBRLItem_ItemId equals c.ItemId
join d in ent.XBRLLabels on a.XBRLItem_ItemId equals d.XBRLItem_ItemId
join e in ent.XBRLItems on b.XBRLItem_ItemId equals e.ItemId
join f in KelompokInformasi on b.XBRLItem_ItemId equals (int)f.XBRLItem_ItemId
where (b.XBRLItem_ItemId == (int)f.XBRLItem_ItemId)
select new MappingDomainRepository
{
KI = f.Id,
Dimension = e.Name,
Domain = c.Id,
Description = d.Text
}).ToList();
Where _list is from List<MappingDomainRepository> _list = new List<MappingDomainRepository>();
in my code above, i want to join my _list to var KelompokInformasi. In var kelompokInformasi I've got 47 rows but in _list I've got 0 data return.
What's wrong in my code? is it possible to join my _list to var kelompokInformasi?

You need to change the second part to:
var other = (from a in ent.XBRLDefinitionRoleDomainItems
join b in ent.XBRLDefinitionRoleDimensionItems on a.XBRLDefinitionRole_DefinitionRoleId equals b.XBRLDefinitionRole_DefinitionRoleId
join c in ent.XBRLItems on a.XBRLItem_ItemId equals c.ItemId
join d in ent.XBRLLabels on a.XBRLItem_ItemId equals d.XBRLItem_ItemId
join e in ent.XBRLItems on b.XBRLItem_ItemId equals e.ItemId
join f in KelompokInformasi on b.XBRLItem_ItemId equals (int)f.XBRLItem_ItemId
where (b.XBRLItem_ItemId == (int)f.XBRLItem_ItemId)
select new MappingDomainRepository
{
KI = f.Id,
Dimension = e.Name,
Domain = c.Id,
Description = d.Text,
XBRLItem_ItemId = a.XBRLItem_ItemId
};
...which adds in the XBRLItem_ItemId which use to join to the CTE.
Then join the two together. We have other (above) and KelompokInformasi from the CTE:
var result = from x in KelompokInformasi
join o in other on x.XBRLItem_ItemId equals o.XBRLItem_ItemId
select new {KelompokInformasi = o.KelompokInformasi,
DimensionName = o.Name,
Domain = o.Id,
Description = o.Text
};
..which appears to be the columns you exentually select.

How can i join two table in Linq and display the join to Data GridView?

I'm trying to join two tables and to display the Join result into GridView in WinForms, but something is going wrong...
it's not giving me Error message or something, Please help!!
my code :
var temp = teacherCmbBx.SelectedItem.ToString();
var temp2 = (from c in context.Teachers
where temp == c.FirstName
select c).ToList();
long num = temp2[0].ID;
var teacherGroup = (from t in context.Teachers
join g in context.Groups on t.ID equals g.TeacherID
where num == t.ID
select t);
teachergrpGridView.DataSource = teacherGroup;
string temp3 = (string)teachergrpGridView.Rows[rowNum].Cells[0].Value;

You are almost there. You are just missing .ToList()
var teacherGroup = (from t in context.Teachers
join g in context.Groups on t.ID equals g.TeacherID
where num == t.ID
select t).ToList();
teachergrpGridView.DataSource = teacherGroup;

var teacherGroup = from t in context.Teachers
join g in context.Groups on t.ID equals g.TeacherID
where num == t.ID
select new {
t.Id ,
g.Name,
t.xxxx
};

LINQ to Entities multiple join

Hi im trying to replicate this mysql query
SELECT a.id, a.title, a.description, a.categories_id, c.name, d.title
FROM ads AS a
INNER JOIN locations AS b
ON a.locations_id = b.id
INNER JOIN areas AS c
ON b.areas_id = c.id
INNER JOIN categories AS d
ON a.categories_id = d.id
WHERE a.title LIKE '%mini%'
AND c.name = 'Fyn'
LIMIT 10
and here is it in LINQ
var query = (from a in db.ads
join b in db.locations on a.locations_id equals b.id
join c in db.areas on b.id equals c.id
join d in db.categories on a.categories_id equals d.id
where a.title.Contains(searchQuery) && c.name.Equals(area)
select new {
a.id,
a.title,
a.description,
category = d.title
}).Take(10);
it doesn't show any error but it's not returning any data.

You have mistake in third line:
join c in db.areas on b.id equals c.id
should be
join c in db.areas on b.areas_id equals c.id