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Linq EF group by to get latest entries into list of objects

I am trying to move from simple SQL to EF.
But there are some complex queries(joins) that it seems to hard to generate the linq for.
At first I tried to use sqltolinq tool to generate the linq but it gives error as some of the things are not supported in the query.
here is the linq:
var entryPoint = (from ep in dbContext.tbl_EntryPoint
join e in dbContext.tbl_Entry on ep.EID equals e.EID
join t in dbContext.tbl_Title on e.TID equals t.TID
where e.OwnerID == user.UID
select new {
UID = e.OwnerID,
TID = e.TID,
Title = t.Title,
EID = e.EID
});
The table entry has many entries that I would like to group and get the latest for each group. But then I would need to select into a view model object which will be bind to gridview.
I dont know where I can implement the logic to group by and get the latest from each and be able to get values from join table into viewModel object.
somewhere I need to add
group entry by new
{
entry.aID,
entry.bCode,
entry.Date,
entry.FCode
}
into groups
select groups.OrderByDescending(p => p.ID).First()
in the above linq to retrieve latest from each group.

You can insert group by right after the joins:
var query =
from ep in dbContext.tbl_EntryPoint
join e in dbContext.tbl_Entry on ep.EID equals e.EID
join t in dbContext.tbl_Title on e.TID equals t.TID
where e.OwnerID == user.UID
group new { ep, e, t } by new { e.aID, e.bCode, e.Date, e.FCode } into g
let r = g.OrderByDescending(x => x.e.ID).FirstOrDefault()
select new
{
UID = r.e.OwnerID,
TID = r.e.TID,
Title = r.t.Title,
EID = r.e.EID
};
The trick here is to include what you need after the grouping between group and by.
However, the above will be translated to CROSS APPLY with all joins included twice. If the grouping key contains fields from just one table, it could be better to perform the grouping/selecting the last grouping element first, and then join the result with the rest:
var query =
from e in (from e in dbContext.tbl_Entry
where e.OwnerID == user.UID
group e by new { e.aID, e.bCode, e.Date, e.FCode } into g
select g.OrderByDescending(e => e.ID).FirstOrDefault())
join ep in dbContext.tbl_EntryPoint on e.EID equals ep.EID
join t in dbContext.tbl_Title on e.TID equals t.TID
select new
{
UID = e.OwnerID,
TID = e.TID,
Title = t.Title,
EID = e.EID
};

SQL query into LINQ in asp.net mvc

Please anyone can help me to write this sql query into Linq. i have tried..
this is my sql query
select o.OrderID,o.Nature,o.Date,od.TotalPrice,os.OrderStatus,lo.FirstName,lo.EmailAddress,lo.PhoneNumber
from [dbo].[Order] o
inner join [dbo].[tbl_OrderDetails] od on od.OrderID = o.OrderID
inner join [dbo].[tbl_OrderHistory] oh on oh.OrderID = o.OrderID
inner join [dbo].[tbl_Login] lo on o.UserID = lo.UserID
inner join dbo.tbl_OrderStatus os on oh.OrderStatusID= os.OrderStatusID
group by o.OrderID,o.Nature,od.TotalPrice,o.Date,os.OrderStatus,lo.FirstName,lo.EmailAddress,lo.PhoneNumber
and this is my try
public override orderDetailModel orderDetails(int id)
{
var results = from o in obj.Orders
join od in obj.tbl_OrderDetails on o.OrderID equals od.OrderID
join oh in obj.tbl_OrderHistory on o.OrderID equals oh.OrderID
join l in obj.tbl_Login on o.UserID equals l.UserID
join os in obj.tbl_OrderStatus on oh.OrderStatusID equals os.OrderStatusID
where (od.OrderID == id)
group o by new { o.Nature, o.OrderID } into
select new orderDetailModel
{
OrderID = o.OrderID,
OrderStatus = os.OrderStatus,
Date = o.Date,
DeliveryNature = o.Nature,
EmailAddress = l.EmailAddress,
FirstName = l.FirstName,
PhoneNumber = l.PhoneNumber,
TotalPrice = od.TotalPrice
};
//group o by new {o.OrderID};
orderDetailModel data = (orderDetailModel)results.FirstOrDefault();
return data;
}
but this is wrong query its not working fine please help me

You need to correct the group by clause, like you have in the SQL query like this:-
group new { o, l } by new { o.OrderID,o.Nature,od.TotalPrice,o.Date,os.OrderStatus,
l.FirstName, l.EmailAddress,l.PhoneNumber } into g
select new orderDetailModel
{
OrderID = g.Key.OrderID,
OrderStatus = g.Key.OrderStatus,
Date = g.Key.Date,
..and so on
};
Since you need the grouping on two tables Order & tbl_Login you will have to first project them as anonymous type group new { o, l } then specify all the groupings and finally while projecting use Key to get the respective items.

I guess that actually, also the SQL query is not correct.
I would simply use a SELECT DISTINCT ... instead of Grouping all the columns.
Anyway, first thing to do:
Check if databases is designed correctly. As far as i can see, if you're joining the table with their Ids, i don't understand why you need to group all the data. If you have duplicates, maybe the error is in the Database design.
If you can't change your Database, or you are happy with it, then use the following LINQ approach:
var distinctKeys = allOrderDetails.Select(o => new { o.OrderID, o.Nature, o.TotalPrice, o.Date,o.OrderStatus,o.FirstName, o.EmailAddress,o.PhoneNumber }).Distinct();
var joined = from e in allOrderDetails
join d in distinctKeys
on new { o.OrderID, o.Nature,o.TotalPrice, o.Date,o.OrderStatus, o.FirstName, o.EmailAddress, o.PhoneNumber } equals d select e;
joined.ToList(); // gives you the distinct/grouped list

Converting left outer join on two queries to LINQ

I have below sql query which I want to convert into LINQ to obtain exactly same results and returned by below query
select *
from (
select distinct DocID
from UserViewDoc
where UserViewDoc.UVID in (102558)) a
left outer join
(
select distinct UserViewDoc.DocID
from UserViewDoc
inner join UserViewHeader on UserViewDoc.UVID = UserViewHeader.UVID
where UserViewDoc.UVID not in (102558)
and UserViewHeader.IsLock = 1) b on a.DocID = b.DocID
where b.DocID is null
)
What I have tried so far is below LINQ statement
var v = (from uvd in this.ViewSelectorControl.LDReviewContext.GetTable<UserViewDoc>()
where IDs.Contains(uvd.UVID)
select new { uvd.DocID, uvd.UVID });
var c = ((from uvd in this.ViewSelectorControl.LDReviewContext.GetTable<UserViewDoc>()
join uvh in this.ViewSelectorControl.LDReviewContext.GetTable<UserViewHeader>() on uvd.UVID equals uvh.UVID
where !IDs.Contains(uvh.UVID) && uvh.IsLock == true
select new { uvd.DocID, uvd.UVID } ));
var d = (from id in v
join ids in c on id.UVID equals ids.UVID into vc
from sub in vc.DefaultIfEmpty()
where sub == null
select id);
The problem I am facing is running the SQL query is returning 30583 records and LINQ version of it is returning all of the 30613 records

I rewrote the query to be exactly like the sql query, i believe that this is the way:
var firstQuery = (from u in this.ViewSelectorControl.LDReviewContext.GetTable<UserViewDoc>()
where IDs.Contains(u.UVID)
select u.DocID).Distinct();
var innerQuery = (from u in this.ViewSelectorControl.LDReviewContext.GetTable<UserViewDoc>()
join uvh in this.ViewSelectorControl.LDReviewContext.GetTable<UserViewHeader>() on uvh.UVID equals u.UVID
where IDs.Contains(u.UIVD) == false
&& uvh.IsLock
select u.DocID).Distinct();
var resultQuery = from f in firstQuery
join i in innerQuery on i equals f into lout
from i in lout.DefaultIfEmpty()
where i == null
select f;

Why don't my SQL results match my Linq results?

When I run this Query in SQL I get what I want:
SELECT Auckland_Park.Formative.[Formative Name]
FROM Auckland_Park.LearningUnit
INNER JOIN Auckland_Park.Formative
ON Auckland_Park.LearningUnit.ID = Auckland_Park.Formative.FK_LU
INNER JOIN Auckland_Park.Reference
INNER JOIN Auckland_Park.Course
ON Auckland_Park.Reference.FK_Course = Auckland_Park.Course.ID
ON Auckland_Park.LearningUnit.ID = Auckland_Park.Reference.FK_LU
WHERE Auckland_Park.Course.Name = 'BI'
My result:
Querying SQL Build
Report Develop
Java App Develop
Andriod App Set up
SharePoint Server
But when I work with my C# app I'm using LINQ to SQL, my LINQ Query looks like this:
//LINQ Query to fill Foramtive Name ComboBox
CTUDataContext data = new CTUDataContext();
var course = (from r in data.LearningUnits
join a in data.Formatives
on r.ID equals a.FK_LU
join f in data.References
on r.ID equals f.FK_LU
join g in data.Courses
on f.FK_LU equals g.ID
where g.Name == ("BI")
select new
{
formativeName = a.Formative_Name,
ID = a.ID
}
).ToList();
txtFormativeName.ItemsSource = course;
txtFormativeName.DisplayMemberPath = "formativeName";
txtFormativeName.SelectedValuePath = "ID";
It seems the same, but I'm not getting the same result that I'm getting with the SQL Query above.

//LINQ Query to fill Foramtive Name ComboBox
CTUDataContext data = new CTUDataContext();
var course = (from r in data.LearningUnits
join a in data.Formatives
on r.ID equals a.FK_LU
join f in data.References
on r.ID equals f.FK_LU
join g in data.Courses
on f.FK_LU equals g.ID
where g.Name == ("BI")
select new
{
formativeName = a.Formative_Name,
ID = a.ID
}
).ToList();
txtFormativeName.ItemsSource = course;
txtFormativeName.DisplayMemberPath = "formativeName";
txtFormativeName.SelectedValuePath = "ID";
ANSWER:
on f.FK_LU equals g.ID
f.FK_LU
must be replaced with
f.FK_Course

Can't access the fields of non-grouping tables in linq

I'm trying to join few tables using LINQ and retrieve a data set. But my problem is when I group the tables, I cannot access the fields of the non grouped tables in the LINQ query. here is my sample code block. Please help
var query = from sb in db.Surfboards
join csb in db.CustomerSurfBoards on sb.SurfBoardID equals csb.SurfBoardID
join c in db.Customers on csb.CustomerID equals c.CustomerID
where c.IsActive
group new { sb,csb} by new {sb.ID, csb.ComponentId} into g
select new ReportModel()
{
ReceivedDate = g.First().Name,
Number = c.First().Number <------- this cannot be accessed
}
what I'm trying to achieve is something like this
select sb.Id, max(c.Number), cbs.Id from Surfboards as sb
inner join CustomerSurfBoards as cbs on sb.SurfBoardID = csb.SurfBoardID
inner join Customers as c on csb.CustomerID = c.CustomerID
group by sb.Id, csb.ComponentId

Try this:
var query = from sb in db.Surfboards
join csb in db.CustomerSurfBoards on sb.SurfBoardID equals csb.SurfBoardID
join c in db.Customers on csb.CustomerID equals c.CustomerID
where c.IsActive
select new {sb.id, c.number, cbs.componentid} into tmp
from t in tmp
group t by new {t.ID, t.ComponentId} into g
select new
{
g.Key.id, g.Key.componentid, number = g.Select(n=>n.number).OrderByDescending().FirstOrDefault()
}