So I've got this linq-to-sql query:
DateTime dtePast = new DateTime(1970, 1, 1);
Datetime newestDate = (from e in tblExpenses
join rd in tblRepairDetails on e.ExpenseItemID equals rd.ExpenseItemID
orderby (DateTime)e.ExpenseDate descending
select e.ExpenseDate).DefaultIfEmpty(dtePast).First();
Without the .First() method, it returns a full list of these 4 dates:
3/18/2013 12:00AM
5/14/2012 12:00AM
2/07/2012 12:00AM
1/10/2012 12:00AM
With the .First() method, however, it returns 1/10/2012 instead of 3/18/2013 as it should. No matter what I try, the oldest date is returned instead of the newest date. How do I get the newest date? I've spent three hours on this and can't figure it out.
==EDIT #1==
Here is the actual code:
DateTime dteNewestOccurrance = (from ve in context.tblVehicleExpenses
join rd in context.tblVehicleRepairDetails on ve.ExpenseItemID equals rd.ExpenseItemID
where ve.VehicleID == strVehicleID && rd.ActivityName == a.ActivityID
orderby (DateTime)ve.ExpenseDate descending
select ve.ExpenseDate).DefaultIfEmpty(dtePast).First();
Again, this code refuses to return the NEWEST date (3/18/2013). I have tried ascending, descending, .OrderByDescending(), etc. and it refuses to give the newest date.
==EDIT #2==
Alright, so after some testing, this code DOES work:
var varOccurranceList = from ve in context.tblVehicleExpenses
join rd in context.tblVehicleRepairDetails on ve.ExpenseItemID equals rd.ExpenseItemID
where ve.VehicleID == strVehicleID && rd.ActivityName == a.ActivityID
orderby (DateTime)ve.ExpenseDate descending
select ve.ExpenseDate;
DateTime dteNewestOccurrance = DateTime.Now;
if (varOccurranceList.Count() > 0)
dteNewestOccurrance = varOccurranceList.First();
else
dteNewestOccurrance = dtePast;
It appears that .DefaultIfEmpty() and/or .First() break the code and result in the unexpected results. I figure either I don't understand how to correctly use these two Linq methods, or there is something horribly wrong with them. I am not happy about this.
Assuming ExpenseDate is nullable, try this:
DateTime dteNewestOccurrance = (from ve in context.tblVehicleExpenses
join rd in context.tblVehicleRepairDetails on ve.ExpenseItemID equals rd.ExpenseItemID
where ve.VehicleID == strVehicleID && rd.ActivityName == a.ActivityID
orderby ve.ExpenseDate descending
select ve.ExpenseDate).FirstOrDefault() ?? dtePast;
Related
I'm having a bit trouble with a query in Linq to Entities which I hope someone can shed a light on :-) What I'm trying to do is to create a query that joins three tables.
So far it works, but since the last table I'm trying to join is empty, the result of the query doesn't contain any records. When I remove the last join, it gives me the right results.
My query looks like this:
var query = from p in db.QuizParticipants
join points in db.ParticipantPoints on p.id
equals points.participantId into participantsGroup
from po in participantsGroup
join winners in db.Winners on p.id
equals winners.participantId into winnersGroup
from w in winnersGroup
where p.hasAttended == 1 && p.weeknumber == weeknumber
select new
{
ParticipantId = p.id,
HasAttended = p.hasAttended,
Weeknumber = p.weeknumber,
UmbracoMemberId = p.umbMemberId,
Points = po.points,
HasWonFirstPrize = w.hasWonFirstPrize,
HasWonVoucher = w.hasWonVoucher
};
What I would like is to get some records even if the Winners table is empty or there is no match in it.
Any help/hint on this is greatly appreciated! :-)
Thanks a lot in advance.
/ Bo
If you set these up as related entities instead of doing joins, I think it will be easier to do what you're trying to do.
var query = from p in db.QuizParticipants
where p.hasAttended == 1 && p.weeknumber == weeknumber
select new
{
ParticipantId = p.id,
HasAttended = p.hasAttended,
Weeknumber = p.weeknumber,
UmbracoMemberId = p.umbMemberId,
Points = p.ParticipantPoints.Sum(pts => pts.points),
HasWonFirstPrize = p.Winners.Any(w => w.hasWonFirstPrize),
HasWonVoucher = p.Winners.Any(w => w.hasWonVoucher)
};
This is assuming hasWonFirstPrize and hasWonVoucher are boolean fields, but you can use any aggregate function to get the results you need, such as p.Winners.Any(w => w.hasWonFirstPrize == 1)
I don't use query syntax a lot but I believe you need to change from w in winnersGroup to from w in winnersGroup.DefaultIfEmpty()
I use EntityFramework 4, LINQ, and C#.
I need display data in a GridView from a query expression using Linq; I need project as anonymous type a value calculate on fly DateTime.UtcNow - cl.DateLocked Note: cl.DateLocked is of type DateTime and I need to know how many days of difference between this two dates.
With this query I receive an error:
DbArithmeticExpression arguments must have a numeric common type.
Any idea how to do it in Linq? If Linq does not allow it how to do it in a different way?
Thanks for your time
var queryContentsLocked = from cl in context.CmsContentsLockedBies
join cnt in context.CmsContents
on cl.ContentId equals cnt.ContentId
join u in context.aspnet_Users
on cl.UserId equals u.UserId
select new
{
cl.DateLocked,
cnt.ContentId,
cnt.Title,
u.UserName,
u.UserId,
TimePan = DateTime.UtcNow - cl.DateLocked // Problem here!!!
};
var queryContentsLocked = from cl in context.CmsContentsLockedBies
join cnt in context.CmsContents
on cl.ContentId equals cnt.ContentId
join u in context.aspnet_Users
on cl.UserId equals u.UserId
select new
{
cl.DateLocked,
cnt.ContentId,
cnt.Title,
u.UserName,
u.UserId,
Days = SqlFunctions.DateDiff("day", cl.DateLocked, DateTime.UtcNow)
};
Without using any SqlFunction
var grandTotalWork = (from t in db.AssignmentHandymandetails
join ad in db.AssignmentDetails on t.assignment_detail_id equals ad.assignment_detail_id
where ad.assignment_id == Convert.ToInt32(Label_assignmentId.Text)
select new { startTime = t.started_time.Value.TimeOfDay, endTime = t.end_time.Value.TimeOfDay, TotalWorkTime = (t.started_time.Value.TimeOfDay.Duration() - t.end_time.Value.TimeOfDay.Duration()).Duration()});
then you can bind the result in GridView you wish
Try this:
DateTime.UtcNow.Subtract(cl.DateLocked).TotalDays
I have the following query to start with:
var query = from p in db.Products
from pc in p.NpProductCategories
where pc.CategoryId == categoryId
select p;
I'm applying some more filtering on it and in the end I want to sort the results:
if (orderBy == ProductSortingEnum.Name)
query = query.OrderBy(x => x.Name);
else
query = query.OrderBy(............);
My big problem (coming from not knowing linq too good) is the ELSE here. How can I sort results by a column that is not in the current result set? I would like to somehow link to another linq query in the orderby. The sorting I'm trying to achive is to link to NpProductVariants query using the ProductId to match between NpProductVariant and Products
and sort by the Price of the NpProductVariant
Assuming you have the relationship set up in the dbml...
For one to one (and many to one):
query = query.OrderBy(p => p.NpProductVariant.Price);
For one to many:
query = query.OrderBy(p => p.NpProductVariants.Select(v => v.Price).Max());
Also:
var query =
from p in db.Products
where p.NpProductCategories.Any(pc => pc.CategoryId == categoryId)
select p;
I think you can hook your Join to your query as long as it is returning the same thing. So maybe something like (I'm not 100 % sure since I haven't tried it):
query = from i1 in query
join i2 in query2 on i1.PropertyToJoin equals i2.PropertyToJoin
orderby i1.OrderProp1, i2.OrderProp2
select i1;
But I think it might be a good idea to check the generated sql so it is still effective.
I wanted to do a paging style table, but NeerDinner example fetches the entire data into a PaggingList type, and I have more than 10 000 rows to be fetched, so I skipped that part.
so I come up with this query
var r = (from p in db.Prizes
join c in db.Calendars on p.calendar_id equals c.calendar_id
join ch in db.Challenges on c.calendar_id equals ch.calendar_id
join ca in db.ChallengeAnswers on ch.challenge_id equals ca.challenge_id
join cr in db.ChallengeResponses on ca.challenge_answer_id equals cr.challenge_answer_id
where
p.prize_id.Equals(prizeId)
&& ch.day >= p.from_day && ch.day <= p.to_day
&& ca.correct.Equals(true)
&& ch.day.Equals(day)
orderby cr.Subscribers.name
select new PossibleWinner()
{
Name = cr.Subscribers.name,
Email = cr.Subscribers.email,
SubscriberId = cr.subscriber_id,
ChallengeDay = ch.day,
Question = ch.question,
Answer = ca.answer
})
.Skip(size * page)
.Take(size);
Problem is, how can I get the total number of results before the Take part?
I was thinking of:
var t = (from p in db.JK_Prizes
join c in db.JK_Calendars on p.calendar_id equals c.calendar_id
join ch in db.JK_Challenges on c.calendar_id equals ch.calendar_id
join ca in db.JK_ChallengeAnswers on ch.challenge_id equals ca.challenge_id
join cr in db.JK_ChallengeResponses on ca.challenge_answer_id equals cr.challenge_answer_id
where
p.prize_id.Equals(prizeId)
&& ch.day >= p.from_day && ch.day <= p.to_day
&& ca.correct.Equals(true)
&& ch.day.Equals(day)
select cr.subscriber_id)
.Count();
but that will do the query all over again...
anyone has suggestions on how can I do this effectively ?
If you take a query as such:
var qry = (from x in y
select x).Count();
...LINQ to SQL will be clever enough to make this a SELECT COUNT query, which is potentially rather efficient (efficiency will depend more on the conditions in the query). Bottom line is that the count operation happens in the database, not in LINQ code.
Writing my old comments :Well i was facing the same issue some time back and then i came up with LINQ to SP =). Make an SP and drop that into your entities and use it.you can get write Sp according to your need like pulling total record column too. It is more easy and fast as compare to that whet you are using wright now.
You can put count for query logic as well as, see the sample as below:
public int GetTotalCountForAllEmployeesByReportsTo(int? reportsTo, string orderBy = default(string), int startRowIndex = default(int), int maximumRows = default(int))
{
//Validate Input
if (reportsTo.IsEmpty())
return GetTotalCountForAllEmployees(orderBy, startRowIndex, maximumRows);
return _DatabaseContext.Employees.Count(employee => reportsTo == null ? employee.ReportsTo == null : employee.ReportsTo == reportsTo);
}
I have some Linq code and it's working fine. It's a query that has a subquery in the Where clause. This subquery is doing a groupby. Works great.
The problem is that I don't know how to grab one of the results from the subquery out of the subquery into the parent.
Frst, here's the code. After that, I'll expplain what piece of data i'm wanting to extract.
var results = (from a in db.tblProducts
where (from r in db.tblReviews
where r.IdUserModified == 1
group r by
new
{
r.tblAddress.IdProductCode_Alpha,
r.tblAddress.IdProductCode_Beta,
r.tblAddress.IdProductCode_Gamma
}
into productGroup
orderby productGroup.Count() descending
select
new
{
productGroup.Key.IdProductCode_Alpha,
productGroup.Key.IdProductCode_Beta,
productGroup.Key.IdProductCode_Gamma,
ReviewCount = productGroup.Count()
}).Take(3)
.Any(
r =>
r.IdProductCode_Alpha== a.IdProductCode_Alpha&&
r.IdProductCode_Beta== a.IdProductCode_Beta&&
r.IdProductCode_Gamma== a.IdProductCode_Gamma)
where a.ProductFirstName == ""
select new {a.IdProduct, a.FullName}).ToList();
Ok. I've changed some field and tables names to protect the innocent. :)
See this last line :-
select new {a.IdProduct, a.FullName}).ToList();
I wish to include in that the ReviewCount (from the subquery). I'm jus not sure how.
To help understand the problem, this is what the data looks like.
Sub Query
IdProductCode_Alpha = 1, IdProductCode_Beta = 2, IdProductCode_Gamma = 3, ReviewCount = 10
... row 2 ...
... row 3 ...
Parent Query
IdProduct = 69, FullName = 'Jon Skeet's Wonder Balm'
So the subquery grabs the actual data i need. The parent query determines the correct product, based on the subquery filters.
EDIT 1: Schema
tblProducts
IdProductCode
FullName
ProductFirstName
tblReviews (each product has zero to many reviews)
IdProduct
IdProductCode_Alpha (can be null)
IdProductCode_Beta (can be null)
IdProductCode_Gamma (can be null)
IdPerson
So i'm trying to find the top 3 products a person has done reviews on.
The linq works perfectly... except i just don't know how to include the COUNT in the parent query (ie. pull that result from the subquery).
Cheers :)
Got it myself. Take note of the double from at the start of the query, then the Any() being replaced by a Where() clause.
var results = (from a in db.tblProducts
from g in (
from r in db.tblReviews
where r.IdUserModified == 1
group r by
new
{
r.tblAddress.IdProductCode_Alpha,
r.tblAddress.IdProductCode_Beta,
r.tblAddress.IdProductCode_Gamma
}
into productGroup
orderby productGroup.Count() descending
select
new
{
productGroup.Key.IdProductCode_Alpha,
productGroup.Key.IdProductCode_Beta,
productGroup.Key.IdProductCode_Gamma,
ReviewCount = productGroup.Count()
})
.Take(3)
Where(g.IdProductCode_Alpha== a.IdProductCode_Alpha&&
g.IdProductCode_Beta== a.IdProductCode_Beta&&
g.IdProductCode_Gamma== a.IdProductCode_Gamma)
where a.ProductFirstName == ""
select new {a.IdProduct, a.FullName, g.ReviewCount}).ToList();
While I don't understand LINQ completely, but wouldn't the JOIN work?
I know my answer doesn't help but it looks like you need a JOIN with the inner table(?).
I agree with shahkalpesh, both about the schema and the join.
You should be able to refactor...
r => r.IdProductCode_Alpha == a.IdProductCode_Alpha &&
r.IdProductCode_Beta == a.IdProductCode_Beta &&
r.IdProductCode_Gamma == a.IdProductCode_Gamma
into an inner join with tblProducts.