I currently have a LINQ query:
public List<EventSchool> GetEventSchools(int eventID)
{
var eventSchools = db.EventSchools
.Include("Organisation")
.Where(e => e.EventID == eventID)
.ToList();
foreach (var ev in eventSchools)
{
if (db.EventSchoolKeyStages.Where(e => e.EventSchoolID == ev.EventSchoolID).Count() > 0)
{
int ks = db.EventSchoolKeyStages
.Where(e => ev.EventSchoolID == ev.EventSchoolID)
.Sum(e => e.Males + e.Females);
ev.StudentNumbers = ks;
}
}
return eventSchools;
}
When I inspect EventSchools, the student numbers for ALL items in the list shows as the first total.
For example, if I have 3 items in the list:
Item 1 - Males = 10, Females = 10
Item 2 - Males = 1, Females = 2
Item 3 - Males = 200, Females = 500
ALL items have a StudentNumbers of 20, rather than:
Item 1 - 20
Item 2 - 3
Item 3 - 700
Not sure what I'm doing wrong?
You have a typo here:
.Where(e => ev.EventSchoolID == ev.EventSchoolID)
This lambda will always be true. I suspect you meant
.Where(e => e.EventSchoolID == ev.EventSchoolID)
^^^
which is different in the indicated place.
You have an error in your query:
.Where(e => ev.EventSchoolID == ev.EventSchoolID)
Should be:
.Where(e => e.EventSchoolID == ev.EventSchoolID)
Related
The following query works, but I want to get the same result without using grp.Sum(). Can we do it?
from item in (await VehicleReplaceCostDataAsync())
group item by (item.type, item.size, item.ADA, item.eseq) into grp
orderby (grp.Key.eseq, grp.Key.size, grp.Key.ADA)
select new VehicleReplacementCost
{
type = grp.Key.type,
size = grp.Key.size,
ADA = grp.Key.ADA,
count = grp.Sum(x => x.count),
cost = grp.Sum(x => x.cost),
Fcount = grp.Sum(x => x.Fcount),
Fcost = grp.Sum(x => x.Fcost),
eseq = grp.Key.eseq,
}).ToList();
Perhaps by using .Aggregate()? [docs]
count = grp.Aggregate(0, (a, b) => a + b.count)
Thanks for the answer from Astrid. It looks like a good one, but I didn't test it. My colleague gave this solution instead by using yield:
var groups = costs
.GroupBy(type => (type.SystemId, type.Type, type.Size, type.ADA, type.Eseq))
.OrderBy(group => (group.Key.SystemId, group.Key.Eseq, group.Key.Size, group.Key.ADA));
foreach (var group in groups)
{
var result = new ProgramGuideVehicleCostRow
{
SystemId = group.Key.SystemId,
Type = group.Key.Type,
Size = group.Key.Size,
ADA = group.Key.ADA,
};
foreach (var row in group)
{
result.Cost += row.Cost;
result.Fcost += row.Fcost;
result.Count += row.Count;
result.Fcount += row.Fcount;
}
yield return result;
}
How do I go about counting missing values using linq. Basically I am counting occurrences within a particular month and I want the count to show as zero if there were no entries for that particular month.
However, currently if there are no entries for that month the array skips a month as shown at index 5 below. The reason I don't want this to happen is because I am plotting the results on a chart so the skipped dates are out of sync from index 5 onwards with the actual count.
Below is my linq query
var veterans = _db.Records
.Where(j => j.Requestor == "Veterans" && EF.Functions.DateDiffMonth(j.Request_Date, DateTime.Now) >= 0 && EF.Functions.DateDiffMonth(j.Request_Date, DateTime.Now) <= 24)
.GroupBy(g => new { g.Request_Date.Value.Year, g.Request_Date.Value.Month }).OrderBy(d => d.Key.Year).ThenBy(d => d.Key.Month)
.Select(group => new
{
Dates = group.Key,
Count = group.Count()
});
var veteransCount = veterans.Select(n => n.Count).ToArray();
You can create a helper function to generate the month+year enumeration you need:
public static IEnumerable<(int Year,int Month)> MonthsInYears(int fromYear, int fromMonth, int toYear, int toMonth) {
for (int year = fromYear; year <= toYear; ++year)
for (int month = (year == fromYear ? fromMonth : 1); month <= (year == toYear ? toMonth : 12); ++month)
yield return (year, month);
}
Then using this, you can create an enumeration of the period:
var veterans = _db.Records
.Where(j => j.Requestor == "Veterans" && EF.Functions.DateDiffMonth(j.Request_Date, DateTime.Now) >= 0 && EF.Functions.DateDiffMonth(j.Request_Date, DateTime.Now) <= 24)
.GroupBy(g => new { g.Request_Date.Value.Year, g.Request_Date.Value.Month }).OrderBy(d => d.Key.Year).ThenBy(d => d.Key.Month)
.Select(group => new {
YearMonth = group.Key,
Count = group.Count()
});
var minYearMonth = veterans.Select(v => v.YearMonth).First();
var maxYearMonth = veterans.Select(v => v.YearMonth).Last();
var monthsInYears = MonthsInYears(minYearMonth.Year, minYearMonth.Month, maxYearMonth.Year, maxYearMonth.Month);
Then you can GroupJoin (as a left join) to your database data:
var veteransCount = monthsInYears.GroupJoin(
veterans,
ym => new { ym.Year, ym.Month },
v => v.YearMonth,
(ym, sj) => sj.FirstOrDefault()?.Count ?? 0)
.ToArray();
Alternatively, since this is a specific case, you could create a Dictionary for your source data and lookup each enumeration value:
var veteransMap = veterans.ToDictionary(v => v.YearMonth, v => v.Count);
var veteransCount2 = monthsInYears.Select(ym => veteransMap.TryGetValue(new { ym.Year, ym.Month }, out var count) ? count : 0)
.ToArray();
NOTE: If you want the full beginning and ending years, you could just call the MonthsInYears method with 1 and 12 for the from and to months.
I have this LINQ query and am getting results I need. However it takes 5-6 seconds to show results on localhost, and I can't even run this on Azure.
I'm new to LINQ, and I'm sure that I'm doing something inefficient.
Could someone direct me to optimize?
var joblist = (from t in db.Tracking
group t by t.JobNumber into j
let id = j.Max(x => x.ScanDate)
select new
{
jn = j.Key,
ti = j.FirstOrDefault(y => y.ScanDate == id).TrackingId,
sd = j.FirstOrDefault(y => y.ScanDate == id).ScanDate,
lc = j.FirstOrDefault(y => y.ScanDate == id).LocationId
}).Where(z => z.lc == lid).Where(z => z.jn != null);
jfilter = (from tr in joblist
join lc in db.Location on tr.lc equals lc.LocationId
join lt in db.LocType on lc.LocationType equals lt.LocationType
select new ScanMod
{
TrackingId = tr.ti,
LocationName = lc.LocationName,
JobNumber = tr.jn,
LocationTypeName = lt.LocationTypeName,
ScanDate = tr.sd,
StoneId = ""
}).OrderByDescending(z => z.ScanDate);
UPDATE:
This query runs on Azure(s1) but it takes 30 seconds. This table has 500,000 rows and I assume that OrderByDescending or FirstOrDefault is killing it...
var joblist = db.Tracking
.GroupBy(j => j.JobNumber)
.Select(g => g.OrderByDescending(j => j.ScanDate).FirstOrDefault());
jfilter = (from tr in joblist
join lc in db.Location on tr.LocationId equals lc.LocationId
join lt in db.LocType on lc.LocationType equals lt.LocationType
where tr.LocationId == lid
select new ScanMod
{
TrackingId = tr.TrackingId,
LocationName = lc.LocationName,
JobNumber = tr.JobNumber,
LocationTypeName = lt.LocationTypeName,
ScanDate = tr.ScanDate,
StoneId = ""
}).OrderByDescending(z => z.ScanDate);
All:
Lets say I have the following table:
RevisionID, Project_ID, Count, Changed_Date
1 2 4 01/01/2016: 01:02:01
2 2 7 01/01/2016: 01:03:01
3 2 8 01/01/2016: 01:04:01
4 2 3 01/01/2016: 01:05:01
5 2 15 01/01/2016: 01:06:01
I am ordering the records based on Updated_Date. A user comes into my site and edits record (RevisionID = 3). For various reasons, using LINQ (with entity framework), I need to get the previous record in the table, which would be RevisionID = 2 so I can perform calculations on "Count". If user went to edit record (RevisionID = 4), I would need to select RevisionID = 3.
I currently have the following:
var x = _db.RevisionHistory
.Where(t => t.Project_ID == input.Project_ID)
.OrderBy(t => t.Changed_Date);
This works in finding the records based on the Project_ID, but how then do I select the record before?
I am trying to do the following, but in one LINQ statement, if possible.
var itemList = from t in _db.RevisionHistory
where t.Project_ID == input.Project_ID
orderby t.Changed_Date
select t;
int h = 0;
foreach (var entry in itemList)
{
if (entry.Revision_ID == input.Revision_ID)
{
break;
}
h = entry.Revision_ID;
}
var previousEntry = _db.RevisionHistory.Find(h);
Here is the correct single query equivalent of your code:
var previousEntry = (
from r1 in db.RevisionHistory
where r1.Project_ID == input.Project_ID && r1.Revision_ID == input.Revision_ID
from r2 in db.RevisionHistory
where r2.Project_ID == r1.Project_ID && r2.Changed_Date < r1.Changed_Date
orderby r2.Changed_Date descending
select r2
).FirstOrDefault();
which generates the following SQL query:
SELECT TOP (1)
[Project1].[Revision_ID] AS [Revision_ID],
[Project1].[Project_ID] AS [Project_ID],
[Project1].[Count] AS [Count],
[Project1].[Changed_Date] AS [Changed_Date]
FROM ( SELECT
[Extent2].[Revision_ID] AS [Revision_ID],
[Extent2].[Project_ID] AS [Project_ID],
[Extent2].[Count] AS [Count],
[Extent2].[Changed_Date] AS [Changed_Date]
FROM [dbo].[RevisionHistories] AS [Extent1]
INNER JOIN [dbo].[RevisionHistories] AS [Extent2] ON [Extent2].[Project_ID] = [Extent1].[Project_ID]
WHERE ([Extent1].[Project_ID] = #p__linq__0) AND ([Extent1].[Revision_ID] = #p__linq__1) AND ([Extent2].[Changed_Date] < [Extent1].[Changed_Date])
) AS [Project1]
ORDER BY [Project1].[Changed_Date] DESC
hope I understood what you want.
Try:
var x = _db.RevisionHistory
.FirstOrDefault(t => t.Project_ID == input.Project_ID && t.Revision_ID == input.Revision_ID -1)
Or, based on what you wrote, but edited:
_db.RevisionHistory
.Where(t => t.Project_ID == input.Project_ID)
.OrderBy(t => t.Changed_Date)
.TakeWhile(t => t.Revision_ID != input.Revision_ID)
.Last()
In my code below, is there any way I can use the results in the object 'WasteRecordsExcluded' to join with searchResults, essentially excluding the WasteId's I don't want.
If I debug to the last line I get the error :
base {System.SystemException} = {"The query contains references to items defined on a different data context."}
Or if joining is impossible then i could change bHazardous from TRUE to FALSE and FALSE to TRUE and do some kind of 'NOT IN' comparison.
Going bananas with this one, anyone help? Kind Regards :
var allWaste = _securityRepository.FindAllWaste(userId, SystemType.W);
var allWasteIndicatorItems = _securityRepository.FindAllWasteIndicatorItems();
// First get all WASTE RECORDS
var searchResults = (from s in allWaste
join x in allWasteIndicatorItems on s.WasteId equals x.WasteId
where (s.Description.Contains(searchText)
&& s.Site.SiteDescription.EndsWith(searchTextSite)
&& (s.CollectedDate >= startDate && s.CollectedDate <= endDate))
&& x.EWC.EndsWith(searchTextEWC)
select s).Distinct();
var results = searchResults;
if (hazardous != "-1")
{
// User has requested to filter on Hazardous or Non Hazardous only rather than Show All
var WasteRecordsExcluded = (from we in _db.WasteIndicatorItems
.Join(_db.WasteIndicators, wii => wii.WasteIndicatorId, wi => wi.WasteIndicatorId, (wii, wi) => new { wasteid = wii.WasteId, wasteindicatorid = wii.WasteIndicatorId, hazardtypeid = wi.HazardTypeId })
.Join(_db.HazardTypes, w => w.hazardtypeid, h => h.HazardTypeId, (w, h) => new { wasteid = w.wasteid, hazardous = h.Hazardous })
.GroupBy(g => new { g.wasteid, g.hazardous })
.Where(g => g.Key.hazardous == bHazardous && g.Count() >= 1)
select we);
// Now join the 2 object to eliminate all the keys that do not apply
results = results.Where(n => WasteRecordsExcluded.All(t2 => n.WasteId == t2.Key.wasteid));
}
return results;
Maybe something like this:
.....
var results = searchResults.ToList();
.....
.....
.Where(g => g.Key.hazardous == bHazardous && g.Count() >= 1)
select we).ToList();
.....