I am using entity framework and doing a group by over a table. My query is a follows:-
var brokerPaymentLists = dbContext.BrokerPayments
.Include("PaymentDetail")
.Where(bp => bp.IdPaymentStatus == (long)EntityModel.Additions.Variables.PaymentStatus.ALLOTED)
.GroupBy(bp => bp.IdBroker,
(key, g) => new
{
IdBroker = key.Value,
BrokerPayments = g.ToList()
}).ToList();
I have included PaymentDetail but after grouping by i can see that the paymentdetail for each item in the BrokerPayments i null. Any suggestion why this is the case, also how can i do the group by such that I can my my paymentDetail insisde each of the BrokerPayments;
The eagerly loading by using Include requires the shape of the data to do not be changed since the Include is applied. In your case this means the query must return IQueryable<BrokerPayments>. But the GroupBy operator changes the shape because it returns IQueryable<IGrouping<TKey, TSource>>. Same will happen with projections and custom joins.
As a workaround you can execute grouping in LINQ to Objects like:
var brokerPaymentLists = dbContext.BrokerPayments
.Include("PaymentDetail")
.Where(bp => bp.IdPaymentStatus == (long)EntityModel.Additions.Variables.PaymentStatus.ALLOTED)
.AsEnumerable()
.GroupBy(bp => bp.IdBroker,
(key, g) => new
{
IdBroker = key.Value,
BrokerPayments = g
});
NOTE: pay attention that the query exectuion will not be defferd
Related
I have an Entity Framework database that I'm querying, so I'm using linq-to-entities.
Here's my query:
// 'Find' is just a wrapper method that returns IQueryable
var q = r.Find(topic =>
topic.PageId != null &&
!topic.Page.IsDeleted &&
topic.Page.IsActive)
// These are standard EF extension methods, which are used to include
linked tables. Note: Page_Topic has a one-to-many relationship with topic.
.Include(topic => topic.Page.Route)
.Include(topic => topic.Page_Topic.Select(pt => pt.Page.Route))
// HERE'S THE QUESTION: This select statement needs to flatten Page_Topic (which it does). But it seems to do it in the wrong place. To explain, if I were to include another column that depended on Page_Topic (for example: 'PillarRoutName2', I'd have to apply the same flattening logic to that column too. Surely the filtering of Page_Topic should be done higher up the query in a DRY way.
.Select(x => new
{
TopicName = x.Name,
HubRouteName = x.Page.Route.Name,
PillarRouteName = x.Page_Topic.FirstOrDefault(y => y.IsPrimary).Page.Route.Name
}).ToList();
Surely the filtering of Page_Topic should be done higher up the query in a DRY way.
Correct! And it's easy to do this:
.Select(x => new
{
TopicName = x.Name,
HubRouteName = x.Page.Route.Name,
FirstTopic = x.Page_Topic.FirstOrDefault(y => y.IsPrimary)
})
.Select(x => new
{
TopicName = x.TopicName,
HubRouteName = x.HubRouteName,
PillarRouteName = x.FirstTopic.Page.Route.Name,
PillarRoutName2 = x.FirstTopic. ...
}).ToList();
Depending on where you start to get properties from FirstTopic you can also use x.Page_Topic.FirstOrDefault(y => y.IsPrimary).Page or .Page.Route in the first part.
Note that you don't need the Includes. They will be ignored because the query is a projection (Select(x => new ...).
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.
The goal is to get the first DateTime and Last DateTime from a collection on an Entity (Foreign Key). My Entity is an organization and my collection are Invoices. I'm grouping results since Organizations unfortunately are not Unique. I'm dealing with duplicate data and cannot assume my organizations are unique so I'm grouping by a Number field on my Entity.
I'm using .NET Core 2.1.2 with Entity Framework.
I'm trying to get the following query generated from LINQ:
SELECT MIN([organization].[Id]) AS Id, MIN([organization].[Name]) AS Name,
MIN([organization].[Number]) AS Number, MIN([invoice].[Date])
AS First, MAX([invoice].[Date]) AS Last
FROM [organization]
INNER JOIN [invoice] ON [invoice].[OrganizationId] = [organization].[Id]
GROUP BY [organization].[Number], [organization].[Name]
ORDER BY [organization].[Name]
However I have no idea how to get to write the LINQ query to get it to generate this result.
I got as far as:
await _context
.Organization
.Where(z => z.Invoices.Any())
.GroupBy(organization => new
{
organization.Number,
organization.Name
})
.Select(grouping => new
{
Id = grouping.Min(organization => organization.Id),
Name = grouping.Min(organization => organization.Name),
Number= grouping.Min(organization => organization.Number),
//First = ?,
//Last = ?
})
.OrderBy(z => z.Name)
.ToListAsync();
I have no clue how to write the LINQ query in such a way that it generates the above.
I have a couple questions still:
Are the Min statements for Id, Name and Number correct ways of getting the
first element in the grouping?
Do I need a join statement or is "WHERE EXISTS" better (this got generated before I changed the code)?
Does anyone know how to finish writing the LINQ statement? Because I have to get the first and last Date from the Invoices Collection on my Organization Entity:
organization.Invoices.Min(invoice => invoice.Date)
organization.Invoices.Max(invoice => invoice.Date)
Here is the trick.
To make inner join by using collection navigation property simple use SelectMany and project all primitive properties that you need later (this is important for the current EF Core query translator). Then perform the GroupBy and project the key properties / aggregates. Finally do the ordering.
So
var query = _context
.Organization
.SelectMany(organization => organization.Invoices, (organization, invoice) => new
{
organization.Id,
organization.Number,
organization.Name,
invoice.Date
})
.GroupBy(e => new
{
e.Number,
e.Name
})
.Select(g => new
{
Id = g.Min(e => e.Id),
Name = g.Key.Name,
Number = g.Key.Number,
First = g.Min(e => e.Date),
Last = g.Max(e => e.Date),
})
.OrderBy(e => e.Name);
is translated to
SELECT MIN([organization].[Id]) AS [Id], [organization].[Name], [organization].[Number],
MIN([organization.Invoice].[Date]) AS [First], MAX([organization.Invoice].[Date]) AS [Last]
FROM [Organization] AS [organization]
INNER JOIN [Invoice] AS [organization.Invoice] ON [organization].[Id] = [organization.Invoice].[OrganizationId]
GROUP BY [organization].[Number], [organization].[Name]
ORDER BY [organization].[Name]
SELECT
[TimeStampDate]
,[User]
,count(*) as [Usage]
FROM [EFDP_Dev].[Admin].[AuditLog]
WHERE [target] = '995fc819-954a-49af-b056-387e11a8875d'
GROUP BY [Target], [User] ,[TimeStampDate]
ORDER BY [Target]
My database table has the columns User, TimeStampDate, and Target (which is a GUID).
I want to retrieve all items for each date for each user and display count of entries.
The above SQL query works. How can I convert it into LINQ to SQL? Am using EF 6.1 and my entity class in C# has all the above columns.
Create Filter basically returns an IQueryable of the entire AuditLogSet :
using (var filter = auditLogRepository.CreateFilter())
{
var query = filter.All
.Where(it => it.Target == '995fc819-954a-49af-b056-387e11a8875d')
.GroupBy(i => i.Target, i => i.User, i => i.TimeStamp);
audits = query.ToList();
}
Am not being allowed to group by on 3 columns in LINQ and I am also not sure how to select like the above SQL query with count. Fairly new to LINQ.
You need to specify the group by columns in an anonymous type like this:-
var query = filter.All
.Where(it => it.Target == '995fc819-954a-49af-b056-387e11a8875d')
.GroupBy(x => new { x.User, x.TimeStampDate })
.Select(x => new
{
TimeStampDate= x.Key.TimeStampDate,
User = x.Key.User,
Usage = x.Count()
}).ToList();
Many people find query syntax simpler and easier to read (this might not be the case, I don't know), here's the query syntax version anyway.
var res=(from it in filter.All
where it.Target=="995fc819-954a-49af-b056-387e11a8875d"
group it by new {it.Target, it.User, it.TimeStampDate} into g
orderby g.Key.Target
select new
{
TimeStampDate= g.Key.TimeStampDate,
User=g.Key.User,
Usage=g.Count()
});
EDIT: By the way you don't need to group by Target neither OrderBy, since is already filtered, I'm leaving the exact translation of the query though.
To use GroupBy you need to create an anonymous object like this:
filter.All
.Where(it => it.Target == '995fc819-954a-49af-b056-387e11a8875d')
.GroupBy(i => new { i.Target, i.User, i.TimeStamp });
It is unnecessary to group by target in your original SQL.
filter.All.Where( d => d.Target == "995fc819-954a-49af-b056-387e11a8875d")
.GroupBy(d => new {d.User ,d.TimeStampDate} )
.Select(d => new {
User = d.Key.User,
TimeStampDate = d.Key.TimeStampDate,
Usage = d.Count()
} );
I have a PostInfo table and LikeInfo Table,PostInfo have list of LikeInfo (for post likes).PostInfo table have a NotMapped property named of "LikeCount".
I want select list of PostInfoes and join to LikeInfo table and calcualte count of LikeInfoes of post and fill count of this to LikeCount property.
Here is my sample:
var query = context.PostInfoes.Where(x => x.UserId == userId).Include(x => x.LikeInfoes);
foreach (var item in query)
{
item.LikeCount = item.LikeInfoes.Count;
}
return query.ToList();
That is not good way for me because I do foreach on query and set LikeCount manualy however I dont want/need include full peoperties of LikeInfo table in this case.
I'm finding the best and easy way to fill this property.
Since EF6 does not allow projecting to entity type, you need to use LINQ to Entities query with intermediate anonymous type projection containing all necessary data, then switch to LINQ to Objects (via AsEnumerable()) and do the final projection, using a delegate block to perform the necessary unmapped property fixups:
var result = context.PostInfoes
.Where(x => x.UserId == userId)
.Select(x => new { Info = x, LikeCount = x.LikeInfoes.Count() })
.AsEnumerable()
.Select(x =>
{
x.Info.LikeCount = x.LikeCount;
return x.Info;
})
.ToList();