I am trying very hard but cannot reach my result. I am new to linq. What should be the proper linq query for this sql query. Please help me out of this.
update Teacher set RemainingCredit = RemainingCredit- Course.Credit
from
CourseAssignTeacher
join Course on CourseAssignTeacher.CourseId = Course.Id
join Teacher on CourseAssignTeacher.TeacherId = Teacher.Id
where CourseAssignTeacher.Id = 1
Write a query that selects what you want to update, then use a foreach loop and context.SubmitChanges:
using (DBDataContext db = new DBDataContext())
{
var toUpdate = from cat in db.CourseAssignTeacher
join c in db.Course on cat.CourseId equals c.Id
join t in db.Teacher on cat.TeacherId equals t.Id
where cat.Id = 1
select new { Teacher = t, Course = c, CourseAssignTeacher = cat };
foreach (var x in toUpdate)
{
x.Teacher.RemainingCredit = x.Teacher.RemainingCredit - x.Course.Credit;
}
db.SubmitChanges();
}
Related
I need to convert my SQL statement to LINQ.
SELECT
dbo.Transactions.TypeRefID,
dbo.TransactionItems.ItemRefID,
SUM(dbo.TransactionItems.Quantity) AS Qty
FROM
dbo.TransactionItems
LEFT OUTER JOIN
dbo.Transactions ON dbo.TransactionItems.TransactionRefID = dbo.Transactions.TransactionID
GROUP BY
dbo.Transactions.TypeRefID, dbo.TransactionItems.ItemRefID
HAVING
(dbo.Transactions.TypeRefID = 1)
AND (dbo.TransactionItems.ItemRefID = 5)
I tried converting the above statement into LINQ and this is what I've done.
var query = from t in db.Transaction
join i in db.TransactionItem on t.TransactionID equals i.TransactionRefID
where t.TypeRefID == 1 && i.ItemRefID == 5
group i by new
{
t.TypeRefID,
i.ItemRefID
} into g
select new
{
TypeRefID = g.Key.TypeRefID,
ItemRefID = g.Key.ItemRefID,
Quantity = g.Sum(q => q.Quantity)
};
When I run my code I get error "System.Linq.Queryable.FirstOrDefault(...) returned null"
I'm using it like this
if (query != null)
string qty = query.FirstOrDefault().Quantity.ToString();
The error is called on "query.FirstOrDefault().Quantity.ToString()"
How to avoid this error?
I have a situation where two tables should be joined with multiple columns with or condition. Here, I have a sample of sql query but i was not able to convert it into linq query.
select cm.* from Customer cm
inner join #temp tmp
on cm.CustomerCode = tmp.NewNLKNo or cm.OldAcNo = tmp.OldNLKNo
This is how i have write linq query
await (from cm in Context.CustomerMaster
join li in list.PortalCustomerDetailViewModel
on new { OldNLKNo = cm.OldAcNo, NewNLKNo = cm.CustomerCode } equals new { OldNLKNo = li.OldNLKNo, NewNLKNo = li.NewNLKNo }
select new CustomerInfoViewModel
{
CustomerId = cm.Id,
CustomerCode = cm.CustomerCode,
CustomerFullName = cm.CustomerFullName,
OldCustomerCode = cm.OldCustomerCode,
IsCorporateCustomer = cm.IsCorporateCustomer
}).ToListAsync();
But this query doesn't returns as expected. How do I convert this sql query into linq.
Thank you
You didn't tell if list.PortalCustomerDetailViewModel is some information in the database, or in your local process. It seems that this is in your local process, your query will have to transfer it to the database (maybe that is why it is Tmp in your SQL?)
Requirement: give me all properties of a CustomerMaster for all CustomerMasters where exists at least one PortalCustomerDetailViewModel where
customerMaster.CustomerCode == portalCustomerDetailViewModel.NewNLKNo
|| customerMaster.OldAcNo == portalCustomerDetailViewModel.OldNLKNo
You can't use a normal Join, because a Join works with an AND, you want to work with OR
What you could do, is Select all CustomerMasters where there is any PortalCustomerDetailViewModel that fulfills the provided OR:
I only transfer those properties of list.PortalCustomerDetailViewModel to the database that I need to use in the OR expression:
var checkProperties = list.PortalCustomerDetailViewModel
.Select(portalCustomerDetail => new
{
NewNlkNo = portalCustomerDetail.NewNlkNo,
OldNLKNo = portalCustomerDetail.OldNLKNo,
});
var result = dbContext.CustomerMasters.Where(customerMaster =>
checkProperties.Where(checkProperty =>
customerMaster.CustomerCode == checkProperty.NewNLKNo
|| customerMaster.OldAcNo == checkProperty.OldNLKNo)).Any()))
.Select(customerMaster => new CustomerInfoViewModel
{
Id = customerMaster.Id,
Name = customerMaster.Name,
...
});
In words: from each portalCustomerDetail in list.PortalCustomerDetailViewModel, extract the properties NewNKLNo and OldNLKNo.
Then from the table of CustomerMasters, keep only those customerMasters that have at least one portalCustomerDetail with the properties as described in the OR statement.
From every remaining CustomerMasters, create one new CustomerInfoViewModel containing properties ...
select cm.* from Customer cm
inner join #temp tmp
on cm.CustomerCode = tmp.NewNLKNo or cm.OldAcNo = tmp.OldNLKNo
You don't have to use the join syntax. Adding the predicates in a where clause could get the same result. Try to use the following code:
await (from cm in Context.CustomerMaster
from li in list.PortalCustomerDetailViewModel
where cm.CustomerCode == li.NewNLKNo || cm.OldAcNo = li.OldNLKNo
select new CustomerInfoViewModel
{
CustomerId = cm.Id,
CustomerCode = cm.CustomerCode,
CustomerFullName = cm.CustomerFullName,
OldCustomerCode = cm.OldCustomerCode,
IsCorporateCustomer = cm.IsCorporateCustomer
}).ToListAsync();
var result=_db.Customer
.groupjoin(_db.#temp ,jc=>jc.CustomerCode,c=> c.NewNLKNo,(jc,c)=>{jc,c=c.firstordefault()})
.groupjoin(_db.#temp ,jc2=>jc2.OldAcNo,c2=> c2.OldNLKNo,(jc2,c2)=>{jc2,c2=c2.firstordefault()})
.select(x=> new{
//as you want
}).distinct().tolist();
How can I convert left join to linq script. I have a T-SQL like this:
SELECT
es.StandardID,
COUNT(DISTINCT esc.StandardCourseID) AS CourseIDCount,
COUNT(DISTINCT esp.StandardPostID) AS PostIDCount
FROM EduStandards AS es
LEFT JOIN EduStandardCourses AS esc
ON es.StandardID = esc.StandardID
LEFT JOIN EduStandardPosts AS esp
ON es.StandardID = esp.StandardID
GROUP BY es.StandardID
That I want to convert this to linq.
Following is the query with left join that is replica of your query in linq.
var query = (from es in dbContext.EduStandards
join esc in dbContext.EduStandardCourses on es.StandardID equals esc.StandardID into ssc
from esc in ssc.DefaultIfEmpty()
join esp in dbContext.EduStandardPosts on es.StandardID equals esp.StandardID into ssp
from esp in ssp.DefaultIfEmpty()
select new { StandardId = es.StandardID, CourseCount = ssc.Count(), PostCount = ssp.Count() }).Distinct().ToList();
But I think we need not to apply left join in linq to calculate count. Following optimized linq query will return same result.
var query2 = (from es in dbContext.EduStandards
join esc in dbContext.EduStandardCourses on es.StandardID equals esc.StandardID into ssc
join esp in dbContext.EduStandardPosts on es.StandardID equals esp.StandardID into ssp
select new { StandardId = es.StandardID, CourseCount = ssc.Count(), PostCount = ssp.Count() });
This is what I've come up with
var query = from es in db.EduStandards
join esc1 in db.EduStandardCourses
on es.StandardId equals esc1.StandardId into esc
from c in esc.DefaultIfEmpty()
join esp1 in db.EduStandardPosts
on es.StandardId equals esp1.StandardId into esp
from p in esp.DefaultIfEmpty()
group new { es.StandardId, Course = c, Post = p } by es.StandardId into g
select new
{
StandardId = g.Key,
CourseIdCount = g.Where(x => x.Course != null).Count(),
PostIdCount = g.Where(x => x.Post != null).Count(),
};
However, I'm not entirely sure if it'll work for EF.
You could always do something like this:
var query = from es in db.EduStandards
select new
{
es.StandardId,
CourseIdCount = db.EduStandardCourses.Where(esc => esc.StandardId == es.StandardId).Distinct().Count(),
PostIdCount = db.EduStandardPosts.Where(esp => esp.StandardId == es.StandardId).Distinct().Count()
};
Also, I can't attest to the performance of either one of these queries due to the lack of knowledge of your database.
Can anyone help me to translate my sql query to linq? I am not so good in linq can anyone help me out with it please .
select
s.UploadFilename ,
a.ID,
isnull(s.Status_id,1) as 'Status_id' ,
a.CaseID,
a.RecordType,
a.ColumnName,
a.FieldName,
a.OldValue,
a.NewValue,
a.ModifiedBy,
A.ModifiedOn,
isnull(u.UserName,'') as 'UserName'
from [dbo].[AuditTrail] as A
left join Case_Status as s
on s.Case_Id=A.CaseID
left join [dbo].[User] as u
on a.ModifiedOn =u.UserID
where A.CaseID=5338
This is not the answer, my query is big, it was not accepting this query as comment.
This query is not returning records :
var AuditTrailFile = (from AT in db.AuditTrails
join ATCS in db.AssnAuditTrailCaseStatus
on new {ID = AT.ID} equals new { ID = (int)(ATCS.AuditTrialID) }
into ATCS_join
from ATCS in ATCS_join.DefaultIfEmpty()
join CS in db.Case_Status on new { Case_StatusId = (int)(ATCS.CaseStatusID) }
equals new { Case_StatusId = CS.Case_StatusId } into CS_join
from CS in CS_join.DefaultIfEmpty()
where
AT.CaseID == CaseID
orderby
AT.ModifiedOn descending
select new
{
ID = (int?)AT.ID,
Case_StatusId = CS.Case_StatusId != null ? CS.Case_StatusId : 1, //Case_StatusId comes for row whose FieldName=Status Else No Case_StatusId
AT.CaseID,
AT.RecordType,
AT.ColumnName,
AT.FieldName,
AT.OldValue,
AT.NewValue,
AT.ModifiedBy,
UserName = AT.User != null ? AT.User.UserName : "",
AT.ModifiedOn,
UploadFilename = CS.UploadFilename
}).ToList();
Can anyone tell me,how to write this query in LINQ?
select a.UTP_NAME, b.UPS_NAME, c.USS_NAME from
TB_UTILIDADE_PUBLIC_UTP a inner join
TB_UTILIDADE_PUBLIC_SECTOR_UPS b on
a.UPS_ID = b.UPS_ID
inner join TB_UTILIDADE_PUBLIC_SUBSECTOR_USS c
on a.USS_ID = c.USS_ID and a.UPS_ID = c.UPS_ID /* IMPORTANT LINE! */
Thanks.
Creating a new anonymous type allows you to join with multiple criteria
var query = from a in context.TB_UTILIDADE_PUBLIC_UTP
join b in context.TB_UTILIDADE_PUBLIC_SECTOR_UPS
on a.UPS_ID equals b.UPS_ID
join c in context.TB_UTILIDADE_PUBLIC_SUBSECTOR_USS
on new { a.USS_ID, a.UPS_ID } equals new { c.USS_ID, c.UPS_ID }
select new
{
a.UTP_NAME,
b.UPS_NAME,
c.USS_NAME
};