I am having trouble doing multiple counts on a single table in a LINQ query. I am using NHibernate, LINQ to NHibernate and C#.
query is a populated list. I have a table that has a boolean called FullRef. I want to do a LINQ query to give a count of occurances of FullRef = false and FullRef = true on each TrackId. TrackId gets a new row for each time he gets a track.Source == "UserRef".
In the following query I get the correct number count (from the FullRefTrueCount) of FullRef = true, but it gives an unknown wrong number on the FullRefFalseCount.
var query2 = from track in query
where track.Source == "UserRef"
group track by new { TrackId = track.TrackId, FullRef = track.FullRef } into d
select new FullReferrer
{
Customer = d.Key.TrackId,
FullRefFalseCount = d.Where(x => x.FullRef == false).Count(),
FullRefTrueCount = d.Where(x => x.FullRef == true).Count()
};
Anyone have any idea on how to fix it? I am pretty certain the .Where() clause is ignored and the "group by" is screwing me over.
If I could somehow
group track by new { TrackId = track.TrackId, FullRefTrue = track.FullRef, FullRefFalse = !track.FullRef }"
it would work. Is there some way to do this?
you should group by trackId only, if you want results by trackId...
var query2 = query
.Where(m => m.Source == "UserRef")
.GroupBy(m => m.TrackId)
.Select(g => new FullReferrer {
Customer = g.Key,
FullRefFalseCount = g.Count(x => !x.FullRef),
FullRefTrueCount = g.Count(x => x.FullRef)
});
Related
Hi i develop web app with c#. I have sql query and i convert to linq but it's not working true because of order by
My sql query
Select TOP 3 HastalikIsmi From Hastaliklar group by HastalikIsmi order by Count(*) desc
My linq
public List<HastalikDto> GetHastalikDto()
{
using (SirketDBContext context = new SirketDBContext())
{
var result = from hastalik in context.Hastaliklar
group hastalik by hastalik.HastalikIsmi into isim
select new HastalikDto { HastalikIsmi = isim.Key };
return result.OrderBy(h => h.HastalikIsmi).Take(3).ToList();
}
}
Here's how you can do the order by on the count of each group and take the 3 with the highest count.
var result = context.Hastaliklar
.GroupBy(x => x.HastalikIsmi)
.OrderByDescending(grp => grp.Count())
.Select(grp => grp.Key)
.Take(3)
.ToList();
How would you write a linq query with the following SQL statement. I've tried several methods referenced on stackoverflow but they either don't work with the EF version I'm using (EF core 3.5.1) or the DBMS (SQL Server).
select a.ProductID, a.DateTimeStamp, a.LastPrice
from Products a
where a.DateTimeStamp = (select max(DateTimeStamp) from Products where a.ProductID = ProductID)
For reference, a couple that I've tried (both get run-time errors).
var results = _context.Products
.GroupBy(s => s.ProductID)
.Select(s => s.OrderByDescending(x => x.DateTimeStamp).FirstOrDefault());
var results = _context.Products
.GroupBy(x => new { x.ProductID, x.DateTimeStamp })
.SelectMany(y => y.OrderByDescending(z => z.DateTimeStamp).Take(1))
Thanks!
I understand you would like to have a list of the latest prices of each products?
First of all I prefer to use group by option even over 1st query
select a.ProductID, a.DateTimeStamp, a.LastPrice
from Products a
where a.DateTimeStamp IN (select max(DateTimeStamp) from Products group by ProductID)
Later Linq:
var maxDateTimeStamps = _context.Products
.GroupBy(s => s.ProductID)
.Select(s => s.Max(x => x.DateTimeStamp)).ToArray();
var results = _context.Products.Where(s=>maxDateTimeStamps.Contains(s.DateTimeStamp));
-- all assuming that max datetime stamps are unique
I've managed to do it with the following which replicates the correlated sub query in the original post (other than using TOP and order by instead of the Max aggregate), though I feel like there must be a more elegant way to do this.
var results = from x
in _context.Products
where x.DateTimeStamp == (from y
in _context.Products
where y.ProductID == x.ProductID
orderby y.DateTimeStamp descending
select y.DateTimeStamp
).FirstOrDefault()
select x;
I prefer to break up these queries into IQueryable parts, do you can debug each "step".
Something like this:
IQueryable<ProductOrmEntity> pocoPerParentMaxUpdateDates =
entityDbContext.Products
//.Where(itm => itm.x == 1)/*if you need where */
.GroupBy(i => i.ProductID)
.Select(g => new ProductOrmEntity
{
ProductID = g.Key,
DateTimeStamp = g.Max(row => row.DateTimeStamp)
});
//// next line for debugging..do not leave in for production code
var temppocoPerParentMaxUpdateDates = pocoPerParentMaxUpdateDates.ToListAsync(CancellationToken.None);
IQueryable<ProductOrmEntity> filteredChildren =
from itm
in entityDbContext.Products
join pocoMaxUpdateDatePerParent in pocoPerParentMaxUpdateDates
on new { a = itm.DateTimeStamp, b = itm.ProductID }
equals
new { a = pocoMaxUpdateDatePerParent.DateTimeStamp, b = pocoMaxUpdateDatePerParent.ProductID }
// where
;
IEnumerable<ProductOrmEntity> hereIsWhatIWantItems = filteredChildren.ToListAsync(CancellationToken.None);
That last step, I am putting in an anonymous object. You can put the data in a "new ProductOrmEntity() { ProductID = pocoMaxUpdateDatePerParent.ProductID }...or you can get the FULL ProductOrmEntity object. Your original code, I don't know if getting all columns of the Product object is what you want, or only some of the columns of the object.
I trying to translate SQL Query to Linq statement:
SELECT f.BarcodeNumber,m.Name, f.Model, SUM(f.Quantity) as FoundedAssetsQty, ISNULL(a.Quantity,0) as AssetQty
FROM [InventoryDB].[dbo].[FoundedAssets] f
join [InventoryDB].[dbo].[PhisicalStockCheckSheets] p on p.ID = f.PhisicalStockCheckSheetId
join [InventoryDB].[dbo].[Inventories] i on i.ID = p.InventoryId
left join [InventoryDB].[dbo].[Assets] a on a.BarcodeNumber = f.BarcodeNumber
join [InventoryDB].[dbo].[Manufacturers] m on m.ID = f.ManufacturerId
where p.InventoryId = 10
group by f.BarcodeNumber, a.Quantity, f.Model, m.Name
I have no idea how to do it. I tried many ways but I fail. Could anyone help me?
I tried to use Linqer, but when I configure the connection it fails, so I write the linq instruction myself. Finally I found the answer. I have not mentioned the relations between entities but it is not important here.
var summary = _context.FoundedAssets.Include(f => f.Manufacturer).
Include(f => f.Asset).
Include(f => f.PhisicalStockCheckSheet).ThenInclude(f => f.Inventory).
Where(f => f.PhisicalStockCheckSheet.Inventory.ID == id).
Select(x => new InventorySummaryModel()
{
BarcodeNumber = x.BarcodeNumber.Value,
ManufacturerName = x.Manufacturer.Name,
Model = x.Model,
AssetsQuantity = x.Asset.Quantity,
FoundedAssetQuantity = x.Quantity
}).ToList();
var groupedSummary = summary.GroupBy(x => x.BarcodeNumber).Select(x => new InventorySummaryModel()
{
BarcodeNumber = x.First().BarcodeNumber,
ManufacturerName = x.First().ManufacturerName,
Model = x.First().Model,
FoundedAssetQuantity = x.Sum(a => a.FoundedAssetQuantity),
AssetsQuantity = x.First().AssetsQuantity
}).ToList();
Maybe exists any easier approach but this one works properly.
I have a query that work on a great data table. The code for the query is:
var getExtInv = snd.external_invoices.OrderByDescending(x => x.date).ToList();
var query = (from c in getExtInv
join o in snd.invoices on c.idexternal_invoices equals o.id_external_invoice
select new {c.idexternal_invoices,
c.businessname,
o.number,
c.message,
c.price,
c.date,
c.tipologiaPagamento,
c.esitoPagamento,
c.iduser
}).ToList();
I need to filter this query with a number of textbox value that can be empty. An example for one search filter is:
if (txtIdUser.Text != "")
{
int idUserSel = Convert.ToInt32(txtIdUser.Text);
query = query.Where(x => x.iduser == idUserSel).ToList();
}
the problem is that with this approach initially load a very high number of data which then filter based on the presence or absence of textfield filled. In doing so the initial loading time is very long. How can I speed up the process?
Thanks to all
As mentioned, don't use .ToList, .ToArray, .Count, etc. before you are ready to use the results.
int i = 0;
var query = from c in snd.external_invoices.OrderByDescending(x => x.date)
join o in snd.invoices on c.idexternal_invoices equals o.id_external_invoice
select new {c.idexternal_invoices, c.businessname, o.number, c.message,
c.price, c.date, c.tipologiaPagamento, c.esitoPagamento, c.iduser };
if(int.TryParse(txtIdUser.Text, out i) // this will check if text is not empty and valid int
query = query.Where(x => x.iduser == i);
and at the end when you are ready to use the results:
var results = query.ToList();
I'm trying to convert this T-SQL to a LINQ-SQL query:
-- top 3 pros for city
select top 3 description, ispro, COUNT(*) as numberofvotes
from tblProCon
where IdPrimaryCity = #IdPrimaryCity
and IsPro = 1
group by IdPrimaryCity, IsPro, description
union
-- top 3 cons for city
select top 3 description, ispro, COUNT(*) as numberofvotes
from tblProCon
where IdPrimaryCity = #IdPrimaryCity
and IsPro = 0
group by IdPrimaryCity, IsPro, description
order by ispro, numberofvotes desc
Here's what i have so far:
// Construct base query
var query = (from p in db.tblProCons
where p.IdPrimaryCity == idPrimaryCity
group p by new { p.IdPrimaryCity, p.IsPro, p.Description } into g
select new { Description = g.Key, IsPro = g.Any(x => x.IsPro), NumberOfAgrees = g.Count() });
// Split queries based on pro/con, and apply TOP(3)
var pros = query.Where(x => x.IsPro).Take(3);
var cons = query.Where(x => !x.IsPro).Take(3);
result = pros
.Union(cons) // Union pro/cons
.OrderByDescending(x => x.IsPro) // Order #1 - Pro/Con
.ThenByDescending(x => x.NumberOfAgrees) // Order #2 - Number of Agree's
.Select(x => new ProCon // project into cut-down POCO
{
Description = x.Description,
IsPro = x.IsPro
}).ToList();
But she ain't working. :(
x.Description is complaining "Cannot convert source type {IdPrimaryCity:int, IsPro:bool, Description:string} to target type string".
All i want to end up with is a List<ProCon>, having the description (string), and flag indicating if it's a pro or con.
What am i doing wrong?
Nevermind, i got it, the "group" projection was all wrong.
Here's the working solution:
// Construct base query
var query = (from p in db.tblProCons
where p.IdPrimaryCity == idPrimaryCity
group p by new { p.IdPrimaryCity, p.IsPro, p.Description } into g
select new { ProCon = g.Key, NumberOfAgrees = g.Count() });
// Split queries based on pro/con, and apply TOP(3)
var pros = query.Where(x => x.ProCon.IsPro).Take(3);
var cons = query.Where(x => !x.ProCon.IsPro).Take(3);
result = pros
.Union(cons) // Union pro/cons
.OrderByDescending(x => x.ProCon.IsPro) // Order #1 - Pro/Con
.ThenByDescending(x => x.NumberOfAgrees) // Order #2 - Number of Agree's
.Select(x => new ProCon // project into cut-down POCO
{
Description = x.ProCon.Description,
IsPro = x.ProCon.IsPro
}).ToList();