I want to return a list of a certain entity grouped by a certain property, ordered descending by timestamp and paginated (using Skip and Take). What I got is this:
container.CoinMessageSet.Where(
c => c.MessageState != MessageStateType.Closed &&
(c.DonorOperator.OperatorCode.Equals("opcode") ||
c.RecipientOperator.OperatorCode.Equals("opcode"))
).OrderByDescending(c => c.TimeStamp)
.GroupBy(c => c.Reference).Skip(x).Take(100);
Upon execution I got the Exception:
The method 'Skip' is only supported for sorted input in LINQ to Entities.
The method 'OrderBy' must be called before the method 'Skip'.
...I called OrderBy() (albeit Descending) and I called it before Skip()! What am I missing?
You haven't ordered the groups; you need to do that before you can page. For example:
.GroupBy(c => c.Reference).OrderBy(grp => grp.Key).Skip(x).Take(100);
(you can also substitute OrderByDescending if you want the groups in reverse order)
Also: since you are grouping, the order in the original data is largely meaningless; you could probably remove the OrderByDescending(c => c.TimeStamp).
So net result:
var query = container.CoinMessageSet.Where(
c => c.MessageState != MessageStateType.Closed &&
(c.DonorOperator.OperatorCode.Equals("opcode") ||
c.RecipientOperator.OperatorCode.Equals("opcode"))
).GroupBy(c => c.Reference).OrderBy(grp => grp.Key)
.Skip(x).Take(100);
or possibly:
var query = (from c in container.CoinMessageSet
where c.MessageState != MessageStateType.Closed &&
(c.DonorOperator.OperatorCode == "opcode" ||
c.RecipientOperator.OperatorCode == "opcode")
group c by c.Reference into grp
orderby grp.Key
select grp).Skip(x).Take(100);
It is most probably because of the GroupBy after the OrderByDescending.
I think you can try:
container.CoinMessageSet.Where(
c => c.MessageState != MessageStateType.Closed &&
(c.DonorOperator.OperatorCode.Equals("opcode") ||
c.RecipientOperator.OperatorCode.Equals("opcode"))
).OrderByDescending(c => c.TimeStamp)
.GroupBy(c => c.Reference).OrderByDescending(c = > c.Key).Skip(x).Take(100);
Related
I have a pretty complicated linq statement that gets a list of people (using Entity Framework) and I want to add an OrderBy clause to the end, depending on which column the user has clicked on for sorting. I DON'T want to get all the people and then sort as there are potentially alot of people and we also do paging, so getting the data and then sorting/paging is not an option. It must therefore be done using LINQ to EF.
I have managed to get the search criteria that filters based on the status of the user's current vaccination status, but I am unable to "convert" that to an OrderBy statement
The data I am getting relates to COVID vaccinations and whether the person's vaccination status is Full, Partial, Not Disclosed or None.
The Entity Framework LINQ statement with the Where clause looks like this and It is an IQueryable<Person>, not a List<Person>:
people.Where(p => p.Encounters.Where(e =>
e.EncounterItems.Any(ei => ei.PersonAssessments.Any(pa =>
pa.Assessment.Questions.Any(q => q.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase) || q.questioncode.Equals("qIDateP", StringComparison.InvariantCultureIgnoreCase)))))
.OrderByDescending(e => e.servicedt ?? e.planneddt).FirstOrDefault()
.EncounterItems.Where(ei =>
ei.PersonAssessments.Any(pa => pa.Answers.Any(a => a.adate.HasValue && DbFunctions.AddMonths(a.adate, procedureCycleDays) < DateTime.Today &&
(a.Question.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase) || (a.Question.questioncode.Equals("qIDateP", StringComparison.InvariantCultureIgnoreCase)
&& (!pa.Answers.Any(aa => aa.adate.HasValue && aa.Question.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase)))
))))).FirstOrDefault()
!= null)
From the above it will filter the people where their vaccination status is "Overdue". i.e they have done either Partial or Full Vaccination but the cycle for this vaccination has been exceeded. There are 2 questions with questioncode's "qIDateP" (partial) and "qIDateF" (full).
I know the below OrderBy is completly wrong, but I want to do something like this so that all the people with overdue vaccination status's are at the top. I will then add several other OrderBy clauses such as "Current" using the same clause, just chainging the date expression e.g. DbFunctions.AddMonths(a.adate, procedureCycleDays) >= DateTime.Today
people.OrderBy(p => p.Encounters.Where(e =>
e.EncounterItems.Any(ei => ei.PersonAssessments.Any(pa =>
pa.Assessment.Questions.Any(q => q.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase) || q.questioncode.Equals("qIDateP", StringComparison.InvariantCultureIgnoreCase)))))
.OrderByDescending(e => e.servicedt ?? e.planneddt).FirstOrDefault()
.EncounterItems.Where(ei =>
ei.PersonAssessments.Any(pa => pa.Answers.Any(a => a.adate.HasValue && DbFunctions.AddMonths(a.adate, procedureCycleDays) < DateTime.Today &&
(a.Question.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase) || (a.Question.questioncode.Equals("qIDateP", StringComparison.InvariantCultureIgnoreCase)
&& (!pa.Answers.Any(aa => aa.adate.HasValue && aa.Question.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase)))
))))).FirstOrDefault()
!= null)
The Relationships for the EF Models is as follows:
Person => Encounter => EncounterItem => PersonAssessment => Answer
A person can answer multiple Assessments over their life and can change their mind as to whether they want to disclose their vaccination status or not.
NOTE: We are using the latest Entity Framework 6.4.4
I hope someone can help me with the OrderBy clause as Im at a complete loss as to how to achieve this.
------UPDATE 1-------
I have used this so far.
people.OrderBy(p => p.Encounters.Where(
e => e.EncounterItems.Any(
ei => ei.PersonAssessments.Any(
pa => pa.Assessment.Questions.Any(
q => q.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase)
|| q.questioncode.Equals("qIDateP", StringComparison.InvariantCultureIgnoreCase))))).OrderByDescending(e => e.servicedt ?? e.planneddt).FirstOrDefault() // you have 1 Encounters item
.EncounterItems.DefaultIfEmpty().FirstOrDefault(
ei => ei.PersonAssessments.Any(
pa => pa.Answers.Any(
a => a.adate.HasValue
&& DbFunctions.AddMonths(a.adate, procedureCycleDays) < DateTime.Today
&& (a.Question.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase)
|| (a.Question.questioncode.Equals("qIDateP", StringComparison.InvariantCultureIgnoreCase)
&& (!pa.Answers.Any(aa => aa.adate.HasValue && aa.Question.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase)))))))).Encounter.planneddt)
The issue is that all the "Overdue" records are at the bottom, not at the top. If I use OrderByDescending it seems correct. How can I now put all those records at the top with OrderBy instead of OrderByDescending.
------ UPDATE 2 Final Solution ------
After a couple of changes based on Margus answer below I have the final updated OrderBy. I had to OrderBydescending for some reason in order to get the records that I wanted at the top.
people.OrderByDescending(p => p.Encounters.Where(
e => e.EncounterItems.Any(
ei => ei.PersonAssessments.Any(
pa => pa.Assessment.Questions.Any(
q => q.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase)
|| q.questioncode.Equals("qIDateP", StringComparison.InvariantCultureIgnoreCase))))).OrderByDescending(e => e.servicedt ?? e.planneddt).FirstOrDefault() // you have 1 Encounters item.EncounterItems.DefaultIfEmpty().FirstOrDefault(
ei => ei.PersonAssessments.Any(
pa => pa.Answers.Any(
a => a.adate.HasValue
&& DbFunctions.AddMonths(a.adate, procedureCycleDays) < DateTime.Today
&& (a.Question.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase)
|| (a.Question.questioncode.Equals("qIDateP", StringComparison.InvariantCultureIgnoreCase)
&& (!pa.Answers.Any(aa => aa.adate.HasValue && aa.Question.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase)))))))).Encounter.planneddt)
Now Im concerned about the performance lol... But that will be another stackoverflow search :)
Well as far as I can tell you want to use orderBy and then simply fetch the first element, while you could simply fetch the first element with the same predicate dropping O(nlogn) complexity
var result = people.Where(
p => p.Encounters.Where(
e => e.EncounterItems.Any(
ei => ei.PersonAssessments.Any(
pa => pa.Assessment.Questions.Any(
q => q.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase)
|| q.questioncode.Equals("qIDateP", StringComparison.InvariantCultureIgnoreCase)))))
.FirstOrDefault(e => e.servicedt ?? e.planneddt) // you have 1 Encounters item
.EncounterItems.FirstOrDefault(
ei => ei.PersonAssessments.Any(
pa => pa.Answers.Any(
a => a.adate.HasValue
&& DbFunctions.AddMonths(a.adate, procedureCycleDays) < DateTime.Today
&& (a.Question.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase)
|| (a.Question.questioncode.Equals("qIDateP", StringComparison.InvariantCultureIgnoreCase)
&& (!pa.Answers.Any(aa => aa.adate.HasValue && aa.Question.questioncode.Equals("qIDateF", StringComparison.InvariantCultureIgnoreCase)))))))));
I have a highly nested class, and trying to find a single item buried deep within. The following gives me an error "Can't convert type match to bool', although I don't see why it thinks I'm trying to return a boolean.
var match = community.TeamLeagues
.Where(x => x.Seasons
.Where(y => y.Divisions
.Where(z => z.Matches
.Where(a => a.Id == "1234").FirstOrDefault())));
Where by itself returns a (deferred) enumerable of items and cannot as such be used as a condition by the outer Where. What you probably want to do is to use Contains(), Any() or All() inside the outer Wheres that will return the result you're looking for.
Something like this might be what you're after:
var match = community.TeamLeagues.Where(t =>
t.Seasons.Any(
s => s.Divisions.Any(
d => d.Matches.Any(
m => m.Id == "1234")
)));
The Where method needs to evaluate an expression that returns a bool. Your nested Wheres are not doing that - the only Where that is, is the last one a => a.Id == "1234", all the other expressions are returning an IEnumerable.
z.Matches.Where(a => a.Id == "1234").FirstOrDefault() returns a object of type Match(your collection item type of the IEnumerable Matches) (or null), no boolean value. I guess you need to check if there are entires in matches that have a Id 1234. Use Any to evaluate a condition:
var match = community.TeamLeagues.Where(x =>
x.Seasons.Any(y =>
y.Divisions.Any(z =>
z.Matches.Any(a => a.Id == "1234")
)));
[items.Where(x => x.Id == 4).Any() is the same as items.Any(x => x.Id == 4)]
This returns you all TeamLeagues which contain a Season which contain a Division which contain a Match which has a element with the id 1234.
To make it simple you can also use the Matches table directly and using a ViewModel you can represent your view.
like:
var MyViewModel = (from l in Mathes
where l.Id == "1234"
select new MyViewModel
{
Id = l.Id,
MatchName = l.Name,
}).ToList();
Couldn't get it working with linq, but works with query syntax.
var leagueMatch = (from teamLeague in community.TeamLeagues
from season in teamLeague.Seasons
from division in season.Divisions
from match in division.Matches.Where(x => x.Id == "1234")
select match).FirstOrDefault();
I have a LINQ, it works fine. My question is: how to convert it to Lambda Expression?
var searchResults = from study in dataContext.Studies
join location in dataContext.Locations
on study.LocationID equals location.LocationID
join doctorLocation in dataContext.DoctorLocations
on location.LocationID equals doctorLocation.LocationID
join doctor in dataContext.Doctors
on doctorLocation.DoctorID equals doctor.DoctorID
where doctor.DoctorID == doctorId
select study;
I think LINQ is more natural to me (similar to SQL script). However, in this case, I just want to convert it to Lambda Expression, but I could not make it work.
I got stuck at:
var searchResults = dataContext.Studies.Where(x =>
x.Location.DoctorLocations.FirstOrDefault() != null &&
x.Location.DoctorLocations.FirstOrDefault().DoctorID == doctorId);
This only works for FirstOrDefault. Since there are multiple DoctorLocations, I do not how to write this one.
Try this:
var searchResults = dataContext.Studies.Where(x =>
x.Location != null
&& x.Location.DoctorLocations.Any(dl => dl.DoctorID == doctorId));
you will get all Studies related to at least one DoctorLocation with DoctorID equals doctorId
var searchResults = dataContext.Studies
.Include(x => x.Locations)
.Include(x => x.DoctorLocations)
.Include(x => x.Doctors)
.Where(x => x.[InheritedPathToDoctor].DoctorId == id)
.Select(x => x.[InheritedPathToStudy].Study)
.FirstOrDefault() OR .ToList()
I have made a lot of assumptions here as to how you have set up your context. I've assumed it's a relational database and therefore the includes simply means it returns all data. I haven't tested it though so there are probably a few errors.
You require an include for every class and the where is pretty self explanatory.
I have a List that contains Supplier data and I would like to search it by using SupplierID, non-active supplier and only 1 latest result.
So I've got:
List<Supplier> filteredList = this.toList();
filteredList.OrderByDescending(m => m.ModifiedDatetime).FirstOrDefault();
filteredList.Where(f => (f.Active == false && f.FieldId == SupplierFieldID))
.ToList<Supplier>();
But I can't make this work; please help.
You need to chain your LINQ expressions, like this:
var filteredList = unfilteredData
.Where(f => f.Active == false && f.FieldId == SupplierFieldID)
.OrderByDescending(m => m.ModifiedDatetime)
.FirstOrDefault();
You do not need a ToList(), because you need a single item, not a list; this is what FirstOrDefault() does. If you need the last item, you need to order by the reverse of your original ordering condition. For example, if you would like the entry with the latest modified date, you need to order by descending (as you did).
You can do this in one statement, chaining together the LINQ operators:
var filteredList = myList.Where(f => f.Active == false && f.FieldId == SupplierFieldID)
.OrderByDescending(m => m.ModifiedDatetime)
.Take(1);
or as #Preston Guillot suggested, the even shorter form:
var filteredList = unfilteredData
.OrderByDescending(m => m.ModifiedDatetime)
.FirstOrDefault(f => f.Active == false && f.FieldId == SupplierFieldID);
I have this Query :
return (from r in this.Requests where r.Status == "Authorised" from i in r.Items select i).Sum(i => i.Value);
I tried converting it to lambda as I prefer that now, so I did :
var sum = Requests.Where(x=>x.Status == "Authorised").Select(x=>x.Items).Sum(x=>x.Value); --> and here I got no Value Item, any ideas why?
You need SelectMany instead of Select. Your query is basically equivalent to:
return this.Requests
.Where(r => r.Status == "Authorised")
.SelectMany(r => r.Items)
.Sum(i => i.Value);
Note that your original query would have been clearer on multiple lines too...