var itemSet = from item in da.GetList<Models.account>()
join file in objFileStorageList
on item.account_id equals file.parent_id into objFile
from fileItem in objFile.DefaultIfEmpty()
where item.company != null && item.company.company_id == 123
orderby item.updatedDate descending
select
new
{
Id = item.account_id,
RefNo = item.refNo,
StartDate = item.StartDate ,
EndDate = item.EndDate ,
Comment = item.comment,
FileStorageID = fileItem != null ? fileItem.fileStorage_id : -1,
Identification = fileItem != null ? fileItem.identifier : null,
fileName = fileItem != null ? fileItem.file_nm : null
};
It raises error message when I try to enumerate through collection result from Linq query above.
LINQ to Entities does not recognize
the method
'System.Collections.Generic.IEnumerable1[SCEFramework.Models.fileStorage]
DefaultIfEmpty[fileStorage](System.Collections.Generic.IEnumerable1[SCEFramework.Models.fileStorage])'
method, and this method cannot be
translated into a store expression
foreach (var item in itemSet)
{
string itemRef= item.RefNo;
}
Please suggest me any solutions.
Thanks in advance.
I think the problem with this is the following 'from' clause:
from fileItem in objFile.DefaultIfEmpty()
Note that your LINQ query may only be executed at the time the result collection is executed. So while you think your exception is in the foreach, it's actually within your expression. This breaks because the possible null value of objFile.DefaultIfEmpty() cannot cast into an IEnumerable.
Try removing the DefaultIfEmpty call and see what happens.
Related
For the following query:
var result = from sch in schemeDashboard
join exp in Expenditure on sch.schemeId equals exp.SchemeCode
into SchExpGroup
where sch.SectorDepartmentId == selectedDepartmentId &&
sch.YearCode == StateManager.CurrentYear
orderby sch.ADPId
select new
{
ModifiedAmounts = SchExpGroup.Select(a => a.ModifiedAmounts),
ProjectName = sch.schemeName,
ADPNo = sch.ADPId,
Allocation = sch.CurrentAllocation,
Expenditures = from expend in SchExpGroup
where expend.YearCode == StateManager.CurrentYear &&
expend.DepartmentId == selectedDepartmentId &&
InvStatus.Contains(expend.Status)
orderby expend.ADPId
group expend by expend.InvoiceId
};
I want to filter the above query on a condition so that result gives only those records where "ModifiedAmounts" are not null. I have tried as follow:
if (rbList2.SelectedIndex == 6)
{
result = result.Where(a => a.ModifiedAmounts != null));
}
but this gives error as:
Cannot compare elements of type
'System.Collections.Generic.IEnumerable`1'. Only primitive types,
enumeration types and entity types are supported.
Any suggestions as I am lost as how to rephrase the filtered query.
I think the problem is that ModifiedAmounts will never be null. Select will return an empty list. Unless SchExpGroup is null in which case you will get a null reference exception.
Try changing your code to
result = result.Where(a => a.ModifiedAmounts.Any());
if (rbList2.SelectedIndex == 6)
{
result = result.Where(a => a.!ModifiedAmounts.Any());
}
My code is as below:
var conntionRecord1Id = (from connectionBase in orgServiceContext.CreateQuery("connection")
where connectionBase["record1roleid"] == null
select new { OpportunityId = connectionBase["record1id"] }).Distinct().ToList();
var query =
from opportunity in orgServiceContext.CreateQuery("opportunity")
orderby opportunity["createdon"] ascending
select new
{
Topic = opportunity.Attributes.Contains("name") == true ? opportunity["name"] : null,
OpportunityId = opportunity.Attributes.Contains("opportunityid") == true ? opportunity["opportunityid"] : null,
PostalCode = opportunity.Attributes.Contains("new_address_postalcode") == true ? opportunity["new_address_postalcode"] : null,
};
var result = (from f in query.ToList() where conntionRecord1Id.Contains(f.OpportunityId) select f).ToList();
But in above query where i am using Contains it giving count 0. even though I have common records in the list
The Contains Linq extension method does not know how to compare complex objects.
Comparing f.OpportunityId to a list of Guids instead of a list of an anonymous type will work:
var conntionRecord1Id = (from connectionBase in orgServiceContext
.CreateQuery("connection")
where connectionBase["record1roleid"] == null
select connectionBase.GetAttributeValue<Guid?>("record1id"))
.Distinct()
.ToList();
Implement IEqualityComparer in a custom comparer class to compare complex objects: https://stackoverflow.com/a/6694563/1817350
Keep in mind that calling .ToList() brings down all the records into memory and will cause performance problems with large amounts of records.
I have a linq query like this :
var trfplanList = (from at in entities.tdp_ProviderAccomodationType
join ap in entities.tdp_ProviderAccomodationTariffPlan on at.PATID equals ap.FK_PATID
join ac in entities.tdp_ProviderAccomodationCategory on ap.FK_PACID equals ac.PACID
where at.FK_ProviderID == CityID && at.IsApproved == 0 && ap.IsApproved == 0 && ac.AccomodationCategory == "Double Occupy"
orderby at.AccomodationType,ap.FromDate,ap.SType
select new AccomodationTariff
{
AccomodationType = at.AccomodationType,
SType = ap.SType,
FromDate = Convert.ToDateTime(ap.FromDate),
ToDate = Convert.ToDateTime(ap.ToDate),
RoomTariff = Convert.ToDecimal(ap.Rate),
ExPAXRate = Convert.ToDecimal(at.PerPaxRate)
}).ToList();
I have two questions:
Can't I convert value while assigning in the select new {} block ? it is giving me an error in project.
I want use 'case' while selecting ExPAXRate from the database for example in SQL I used to write :
CASE ap.SType WHEN 'Off Season' THEN at.PerPaxRateOS ELSE at.PerPaxRate END AS ExPAXRate
Can I use something like this in linq query ?
Can't I convert value while assigning in the select new {} block
No, you can't (sadly). EF doesn't know how to translate it into SQL.
I want use 'case'
You can use the ternary operator (?):
ExPAXRate = at.OffSeason ? at.PerPaxRateOS : at.PerPaxRate
(assuming that at.OffSeason exists).
A solution for the conversion issue could be to project into an anonymous type first and then, in memory, to AccomodationTariff:
...
select new
{
AccomodationType = at.AccomodationType,
SType = ap.SType,
FromDate = ap.FromDate,
ToDate = ap.ToDate,
RoomTariff = ap.Rate,
ExPAXRate = at.PerPaxRate
}).AsEnumerable()
.Select(x => new AccomodationTariff
{
AccomodationType = x.AccomodationType,
SType = x.SType,
FromDate = Convert.ToDateTime(x.FromDate),
ToDate = Convert.ToDateTime(x.ToDate),
RoomTariff = Convert.ToDecimal(x.Rate),
ExPAXRate = Convert.ToDecimal(x.PerPaxRate)
}).ToList();
I have a problem with the following method:
public IQueryable<Customer> ListCustomers(int? parentId)
{
Debug.Assert(parentId == null);
//var list = _customerRepository.List().Where(c => c.ParentId == null);
var list = _customerRepository.List().Where(c => c.ParentId == parentId);
return list;
}
I have one Customer in my DB with a ParentId of null. When I call the method with ListCustomers(null), list is empty for the return statement. If I swap the commented out line in and query with a hard-coded null, then list contains my one customer.
What could cause this difference between these two queries? Why is the one with c.ParentId == parentId not returning anything?
Becouse the Nullable type the linq provider will not generate the proper IS NULL check. See this answer for further information: https://stackoverflow.com/a/785501/1195510
EF translates your query with int? to something like this:
DECLARE #parentId Int = null
SELECT ... WHERE ParentId = #parentId
When this is executed on the database, it doesn't do what you expect because in SQL [column] = NULL is always false.
I agree EF could handle this better, but as a workaround, you can write something like this:
.Where( c => !parentId.HasValue
? !c.ParentId.HasValue
: c.ParentId.Value == parentId.Value
)
EF will then generate a ( somewhat verbose ) SQL statement with the correct IS NULL predicates.
with nullable types you have to use it like this:
.Where(c=> object.Equals(c.ParentId, parentId))
in this example code
public Company GetCompanyById(Decimal company_id)
{
IQueryable<Company> cmps = from c in db.Companies
where c.active == true &&
c.company_id == company_id
select c;
return cmps.First();
}
How should I handle if there is no data in cmps?
cmps will never be null, so how can I check for non existing data in a LINQ Query?
so I can avoid this
'cmps.ToList()' threw an exception of type ... {System.NullReferenceException}
when transforming it into, for example, a List
GetCompanyById(1).ToList();
Do I always need to wrap it up in a try catch block?
You can use Queryable.Any() (or Enumerable.Any()) to see if there is a member in cmps. This would let you do explicit checking, and handle it however you wish.
If your goal is to just return null if there are no matches, just use FirstOrDefault instead of First in your return statement:
return cmps.FirstOrDefault();
What about applying .Any or .Count() ?
Here's an example on MSDN
List<int> numbers = new List<int> { 1, 2 };
bool hasElements = numbers.Any();
Console.WriteLine("The list {0} empty.",
hasElements ? "is not" : "is");
Or just use the ?: operator
return myExample.Any() ? myExample.First() : null;
This will return the first one if there is one, or null if there isn't:
return (from c in db.Companies
where c.active == true &&
c.company_id == company_id
select c).FirstOrDefault();
Try return cmps.Count()==0?null:cmp.First()
That way if it is null it will simply return a null Company and if its not then it will return the first one in the list.
Check out http://en.wikipedia.org/wiki/Ternary_operation
var context = new AdventureWorksLT2008Entities();
var cust = context.Customers.Where(c => c.CustomerID == 1);
if (cust.Any())
{
Customer c = cust.First();
}