I am trying to select from multiple tables in an entity model. But there are two columns I would like to select and it's just not working out. The LINQ statement I have is:
var searchResult = from i in _imEntities.Issues
join dept in _imEntities.Departments
on i.Issued_to_dept equals dept.Dept_ID
where i.State == 1
select new {
i.ID_No,
i.Issue_Date,
Raised_By = dept.Dept_Name
.Where(i.Raised_by_Dept == dept.Dept_ID),
Issued_To = dept.Dept_Name
.Where(i.Issued_to_dept == dept.Dept_ID),
Details = i.Details
};
The column names are all correct, but I just can't get the dept_Names into the Raised_By and Issued_To fields. Is there another way to execute this?
Try this:
var query = from i in _imEntities.Issues
join dept_r in _imEntities.Departments
on i.Issued_to_dept equals dept_r.Dept_ID
join dept_i in _imEntities.Departments
on i.Issued_to_dept equals dept_i.Dept_ID
where i.State == 1
select new {
i.ID_No,
i.Issue_Date,
Raised_By = dept_r.Dept_Name,
Issued_To = dept_i.Dept_Name,
Details = i.Details
};
It's not clear what you are trying to achieve. But you definitely trying to apply where filter on single name string (also predicate syntax is not correct). Here is query which conditionally returns Dept_Name in Raised_By and Issued_To properties:
var query = from i in _imEntities.Issues
join dept in _imEntities.Departments
on i.Issued_to_dept equals dept.Dept_ID
where i.State == 1
select new {
i.ID_No,
i.Issue_Date,
Raised_By = (i.Raised_by_Dept == dept.Dept_ID) ? dept.Dept_Name : null,
Issued_To = (i.Issued_to_dept == dept.Dept_ID) ? dept.Dept_Name : null,
Details = i.Details
};
Related
I am sql query us producing correct result, but when i'm doing the same in LINQ. Output is incorrect. Please let me know where my making mistake.
Following linq query that i created.
LINQ Query:
List<UserModel> Model = (from users in db.UserM
join ct in db.CustT on users.UserId equals ct.UserID into group1
from g1 in group1.DefaultIfEmpty()
join ti in db.TestIn on g1.TestId equals ti.TestID into group2
from g2 in group2.DefaultIfEmpty()
where (users.CustomerId==CustomerId) && (users.RoleId == 4) && (users.Status == 1)
group new
{
g2.TestInvitationID,
g2.TestID,
}
by new
{
users.FirstName,
users.CreatedOn,
users.Email,
users.UserId
} into group4
select new UserModel
{
Name = group4.Key.FirstName,
CreatedOn = group4.Key.CreatedOn,
EmailId = group4.Key.Email,
UserId = group4.Key.UserId,
NoOfTestTaken = group4.Select(x=>x.TestID).Distinct().Count(),
NoOfInvitationsSent = group4.Count(x => x.TestInvitationID != 0)
}).ToList();
SQL Query:
SELECT IsNull(COUNT(distinct TS.TestId),0) AS NoOfTests,
IsNull(COUNT(TS.TestInvitationID),0) AS NoOfInvitations,
UM.Email,
UM.UserId,
UM.FirstName,
UM.CreatedOn
FROM UserM as UM
left JOIN CustT AS CT
ON UM.UserId=CT.UserId
left JOIN TestIn AS TS
ON TS.TestId = CT.TestId
WHERE UM.CustomerId=41
AND UM.RoleId=4
and UM.[Status]=1
GROUP BY UM.UserId, UM.Email, UM.FirstName, UM.CreatedOn
Tables:
"UserM" - columns: UserId, Email, FirstName, CreatedOn
"CustT" - columns: TestId, UserId,
"TestIn" - columns: TestInvitationId, TestId
The difference between SQL COUNT(expr) and LINQ Count is that the former excludes NULL values, which produces a difference when used on right side of a left outer join with no matching records (SQL will produce 0 while LINQ 1). The closest LINQ equivalent is Count(expr != null).
So the direct translation of your SQL query would be like this (note that the generated SQL query could and most likely will be different):
(A side note: When converting SQL query to LINQ, it's good to use the same aliases to make it easier to see the mappings)
var query =
from um in db.UserMasters
join ct in db.CustTests on um.UserId equals ct.UserID
into ctGroup from ct in ctGroup.DefaultIfEmpty() // left outer join
join ts in db.TestInvitaions on ct.TestId equals ts.TestID
into tsGroup from ts in tsGroup.DefaultIfEmpty() // left outer join
where um.CustomerId == UserSession.CustomerId
&& um.RoleId == 4
&& um.Status == 1
group ts by new { um.UserId, um.Email, um.FirstName, um.CreatedOn } into g
select new UserModel
{
Name = g.Key.FirstName,
CreatedOn = g.Key.CreatedOn,
EmailId = g.Key.Email,
UserId = g.Key.UserId,
NoOfTestTaken = g.Where(ts => ts != null).Select(ts => ts.TestID).Distinct().Count(),
NoOfInvitationsSent = g.Count(ts => ts != null)
};
var result = query.ToList();
I suspect that the following row is the problem because is not the same like in your sql:
Linq:
NoOfInvitationsSent = group4.Count(x => x.TestInvitationID != 0)
SQL:
IsNull(COUNT(TS.TestInvitationID),0) AS NoOfInvitations
Due to counting items from a left join Linq should be instead:
NoOfInvitationsSent = group4.Where(i => i != null).Count()
To put it all together, with a bit of better formatting:
var model = (from users in db.UserMasters
join ct in db.CustTests on users.UserId equals ct.UserID into group1
from ct in group1.DefaultIfEmpty()
join ti in db.TestInvitaions on ct.TestId equals ti.TestID into group2
from ct in group2.DefaultIfEmpty()
where users.CustomerId == UserSession.CustomerId &&
users.RoleId == 4 &&
users.Status == 1
group new { ct.TestInvitationID, ct.TestID }
by new
{
users.FirstName,
users.CreatedOn,
users.Email,
users.UserId
} into grouping
select new UserModel
{
Name = grouping.Key.FirstName,
CreatedOn = grouping.Key.CreatedOn,
EmailId = grouping.Key.Email,
UserId = grouping.Key.UserId,
NoOfTestTaken = grouping.Where(i => i != null).Select(x => x.TestID).Distinct().Count(),
NoOfInvitationsSent = grouping.Where(i => i != null).Count()
}).ToList();
I have a parent table, parentTable which may or may not have children in childTable. I am looking to get average % complete of any given parent's children, and the MAX(due) (date) of the children where they exist. My SQL is this:
SELECT parentRecord_id, assigned_to,
(SELECT avg(complete)
FROM childTable
WHERE parent_id = parentRecord_id
and deleted IS NULL
GROUP BY parent_id),
(SELECT max(due)
FROM childTable
WHERE parent_id = parentRecord_id
and deleted IS NULL
GROUP BY parent_id
)
FROM parentTable s
WHERE s.deleted IS NULL and assigned_to IS NOT NULL
My result set gives me rows with either correct values for the average and max, or null. In this instance I have to do follow up processing so I could ignore the null values if I was doing a foreach through DataTable rows. However I am trying to do this in Linq and can't figure out how to avoid a System.InvalidOperationException where Linq is trying to cast null to a double. Here is what I've tried so far.
var query8 = from s in db.parentTable
where s.deleted == null
select new
{
ID = s.assigned_to,
Average =
((from t in db.childTable
where t.parent_id == s.strategy_id
group t by new { t.parent_id } into g
select new
{
a0 = g.Average(f0 => f0.complete )
}).FirstOrDefault().a0)
};
foreach (var itm in query8)
{
Console.WriteLine(String.Format("User id:{0}, Average: {1}", itm.ID, itm.Average));
}
Here's my question. How do I get the query to handle those returned rows where average complete or max due (date) are null?
You can either filter out the records where the values are null (by another condition) or if you want to include them do something like this:
a0 = g.Average(f0 => f0.complete.HasValue? f0.complete: 0 )
I would cast the list to nullable double before calling Average/Max like so:
var query8 =
from s in db.parentTable
where s.deleted == null
select new
{
ID = s.assigned_to,
Average =
from t in db.childTable
where t.parent_id == s.strategy_id
group t by t.parent_id into g
select g.Cast<double?>().Average(f0 => f0.complete)
};
Assuming complete is a Nullable, you should be able to do:
var query8 = from s in db.parentTable
where s.deleted == null
select new
{
ID = s.assigned_to,
Average =
((from t in db.childTable
where t.parent_id == s.strategy_id
&& s.complete.HasValue()
group t by new { t.parent_id } into g
select new
{
a0 = g.Average(f0 => f0.complete )
}).FirstOrDefault().a0)
};
Thanks to all who responded.
I was unable get around the null anonymous issue with the basic query as I had it, but adding a join to the childTable eliminated the nulls.
Another solution is to use a from x in g.DefaultIfEmpty clause.
var query8 =
from st in db.tableParent
select new { Ass = st.assigned_to ,
Avg =
(from ta in db.tableChild
group ta by ta.parent_id into g
from x in g.DefaultIfEmpty()
select g.Average((f0=>f0.complete))).FirstOrDefault()
};
I have one Linq Query. When I run the query, Only for 10 records its taking 13 seconds to extract the data to the model. I need to know the query which I wrote is good for performance or not. Please guide me what i am doing wrong.
Code
var stocktakelist = (from a in Db.Stocktakes
select new ExportStock
{
Id = a.Id,
ItemNo = a.ItemNo,
AdminId = (from admin in Db.AdminAccounts where admin.Id == a.Id select admin.Name).FirstOrDefault(),
CreatedOn = a.CreatedOn,
Status = (from items in Db.Items where items.ItemNo == a.ItemNo select items.ItemStatu.Description).FirstOrDefault(),
Title = (from tit in Db.BibContents where tit.BibId == (from bibs in Db.Items where bibs.ItemNo == a.ItemNo select bibs.BibId).FirstOrDefault() && tit.TagNo == "245" && tit.Sfld == "a" select tit.Value).FirstOrDefault() // This line of Query only makes the performance Issue
}
).ToList();
Thanks
The reason this is so slow is because it is running the 3 inner LINQ statements for every item in the outer LINQ statement.
Using LINQ joins will run only 4 queries and then link them together, which is faster.
To find out how to join, there are plenty of resources on the Internet depending on the type of LINQ you are using.
If you're retrieving this data from a SQL server, perhaps consider doing this intensive work in SQL - this is what SQL was designed for and it's much quicker than .NET. EDIT: As highlighted below, the work is done in SQL if using LINQ to SQL/Entities and using the correct join syntax.
I was trying to create the corresponding query with some joins for practice.
I cannot test it and i'm not 100% sure that this query will you get the result
you are hoping for but maybe at least it will give you a hint on how to write
joins with linq.
from a in Db.Stocktakes
join admin in Db.AdminAccounts
on a.Id equals admin.Id
into adminJoinData
from adminJoinRecord in adminJoinData.DefaultIfEmpty( )
join items in Db.Items
on a.ItemNo equals items.ItemNo
into itemsJoinData
from itemsJoinRecord in itemsJoinData.DefaultIfEmpty( )
join title in Db.BibContents
(
from subQuery in Db.BibContents
where subQuery.TagNo == "245"
where subQuery.Sfld == "a"
select subquery
)
on title.BibId equals itemsJoinRecord.BidId
into titleJoinData
from titleJoinRecord in titleJoinData.DefaultIfEmpty( )
select new ExportStock( )
{
Id = a.Id,
ItemNo = a.ItemNo,
AdminId = adminJoinRecord.Name,
CreatedOn = a.CreatedOn,
Status = itemsJoinRecord.ImemStatu.Description,
Title = titleJoinRecord.Value
}
As others have said, you should use Left Outer Joins in your LINQ just as you would if writing it in SQL.
Your query above will end up looking roughly like this once converted (this is untested, but gives the basic idea):
var a = from a in Db.Stocktakes
join admin in Db.AdminAccounts on admin.Id equals a.Id into tmpAdmin
from ad in tmpAdmin.DefaultIfEmpty()
join item in Db.Items on item.ItemNo equals a.ItemNo into tmpItem
from it in tmpItem.DefaultIfEmpty()
join title in Db.BibContents on bib.BibId equals items.BibId into tmpTitle
from ti in tmpTitle.DefaultIfEmpty()
where ti.TagNo == "245"
&& ti.Sfld == "a"
select new ExportStock
{
Id = a.Id,
ItemNo = a.ItemNo,
AdminId = ad == null ? default(int?) : ad.Id,
CreatedOn = a.CreatedOn,
Status = it == null ? default(string) : it.ItemStatus.Description,
Title = ti == null ? default(string) : ti.Value
};
Using lambda expressions your query will look like this:
Db.Stocktakes
.Join(Db.AdminAccounts, a => a.Id, b => b.Id, (a,b) => new { a, AdminId = b.Name })
.Join(Db.Items, a => a.ItemNo, b => b.ItemNo, (a,b) => new { a, Status = b.ItemStatus.Description, BidId = b.BibId })
.Join(Db.BibContents, a => a.BibId, b => b.BibId, (a,b) => new { a, Value = b.Value, TagNo = b.TagNo, Sfld = b.Sfld })
.Where(a => a.TagNo == "245" && a.Sfld == "a")
.Select(a =>
new ExportStock { Id = a.Id,
ItemNo = a.ItemNo,
AdminId = a.AdminId,
CreatedOn = a.CreatedOn,
Status = a.Status,
Title = a.Value
}
).ToList();
I would like to join results from a table, to sum up the results from a where condition on 2 different rows, as this code:
var a = (from o in _DB.Services
where (o.description.Contains(searchText) || o.nom.Contains(searchText))
orderby o.date
select new { results = ?????, id = ?????? }).Take(maxResults).ToList();
What can I put, in order to take into account the results=???? and id=???
Thanks
Based on your comment, can't you just do the following?
var a = (from o in _DB.Services
where (o.description.Contains(searchText) || o.nom.Contains(searchText))
orderby o.date
select new
{
results = o.description,
id = o.nom
})
.Take(maxResults)
.ToList();
I have a table of orders. the status is on the soilorders which is joined to the orders.
I only want to return orders where the joined soilorder does not have status "Removed".
I had thought that
join sso in db.SoilSamplingOrders on ord.order_id equals sso.order_id
where sso.status.Equals("Removed")!=true
but then no records are returned!
thanks for any help (query below)
var query =
from ord in db.Orders
join sso in db.SoilSamplingOrders on ord.order_id equals sso.order_id
where sso.status.Equals("Removed")!=true
join cust in db.Customers on ord.customer_id equals cust.customer_id
select new Listing
{
assigned_to = sso.assigned_to,
company = cust.company,
order_id = ord.order_id,
order_created = ord.order_created,
customer_id = ord.customer_id,
order_created_by_employ_id = ord.order_created_by_employ_id,
first_farm_on_order = (from f in db.SoilSamplingSubJobs
where f.order_id == ord.order_id
select new ListingSubJob { first_farm_on_order = f.farm }).
AsEnumerable().First().first_farm_on_order,
total_fields = (from f in db.SoilSamplingSubJobs
where f.order_id == ord.order_id
select new { f.sssj_id }).AsEnumerable().Count(),
total_area = (float?) (from f in db.SoilSamplingSubJobs
where f.order_id == ord.order_id && f.area_ha != null
select f.area_ha ).Sum() ?? 0 ,
total_area_ph_density = (float?)(from f in db.SoilSamplingSubJobs
where f.order_id == ord.order_id && f.ph != null
select f.ph).Sum() ?? 0,
};
DOH! Just as nature abhors a vacuum, anything Null cannot be included in the select. Added values to the status field and bom it works.