I am struggling converting the following SQL query I wrote into Linq. I think I'm on the right track, but I must be missing something.
The error I'm getting right now is:
System.Linq.IQueryable does not contain a definition for .Contains
Which is confusing to me because it should right?
SQL
select Users.*
from Users
where UserID in (select distinct(UserID)
from UserPermission
where SupplierID in (select SupplierID
from UserPermission
where UserID = 6))
LINQ
var Users = (from u in _db.Users
where (from up in _db.UserPermissions select up.UserID)
.Distinct()
.Contains((from up2 in _db.UserPermissions
where up2.UserID == 6
select up2.SupplierID))
select u);
EDIT: I ended up going back to SqlCommand objects as this was something I had to get done today and couldn't waste too much time trying to figure out how to do it the right way with Linq and EF. I hate code hacks :(
I think there is no need to do a distinct here (maybe I am wrong). But here is a simpler version (assuming you have all the navigational properties defined correctly)
var lstUsers = DBContext.Users.Where(
x => x.UserPermissions.Any(
y => y.Suppliers.Any(z => z.UserID == 6)
)
).ToList();
Above if you have UserID field in Supplier entity, if it is NOT you can again use the navigational property as,
var lstUsers = DBContext.Users.Where(
x => x.UserPermissions.Any(
y => y.Suppliers.Any(z => z.User.UserID == 6)
)
).ToList();
Contains() only expects a single element, so it won't work as you have it written. Try this as an alternate:
var Users = _db.Users
.Where(u => _db.UserPermissions
.Select(x => UserID)
.Distinct()
.Where(x => _db.UserPermissions
.Where(y => y.UserID == 6)
.Select(y => y.SupplierID)
.Contains(x))
);
I didn't try on my side but you can try using the let keyword:
var Users = (from u in _db.Users
let distinctUsers = (from up in _db.UserPermissions select up).Distinct()
let subQuery = (from up2 in _db.UserPermissions
where up2.UserID == 6
select up2)
where
distinctUsers.SupplierID== subQuery.SupplierID &&
u.UserID==distinctUsers.UserID
select u);
Related
I'm trying to work out the Entity Framework syntax to return the User.Name, User.Email for the given Profile.email.
1 profile can have N categories. 1 category can have 1 User.
Profile - ID, email, Name, CreatedDate
Category - ID, ProfileId, Name, UserID
User - ID, Name, Email
In SQL I would write:
SELECT U.NAME, U.EMAIL
FROM PROFILE P
JOIN CATEGORY C ON P.ID = C.PROFILEID
JOIN USER U ON C.USERID = U.ID
WHERE P.EMAIL = 'SOME#EMAIL.COM'
Here is what I tried:
var data = await _context.Profiles
.AsNoTracking()
.Where(p => p.Categories.Users.email == 'some#email.com')
.Select(u => new
{
UName = u.Name,
UEmail = u.Email
}).ToListAsync();
The problem is that p.Categories is an ICollection, so I don't know how to proceed because p.Categories doesn't give me access to the .Users. I can write p.Categories.Where.... but I'm not sure how to proceed.
Instead of starting with _context.Profiles. should I be starting with _context.Users.?
Can someone help me on how to think about the approach when writing the Entity Framework query?
If I understood your model correctly, this should work:
var data = await _context.Categories.AsNoTracking()
.Where(c=>c.Profile.email == "some#email.com")
.Select(c=>new {
UName=c.User.Name,
UEmail=c.User.Email
}).ToListAsync();
Ofcourse this requires your model to have navigation properties set.
So just start your query the Categories in LINQ form:
from c in _context.Categories
where c.Profile.Email == someEmail
select new { c.User.Name, c.User.Email }
or in Lambda form:
_context.Categories
.Where( c => c.Profile.Email == someEmail )
.Select( c => new {c.User.Name, c.User.Email}
or start from Profiles and use SelectMany, whose LINQ form looks like
from p in _context.Profiles
from c in p.Categories
where p.Email == someEmail
select new {c.User.Name, c.User.Email}
or in Lambda form:
_context.Profiles
.Where(p => p.Email == someEmail)
.SelectMany(p => p.Categories)
.Select( c => new {c.User.Name, c.User.Email} )
I want to do a simple subquery in LINQ to EF
I did something like this:
from p in db.SomeTable
let o = db.SomeTableWithDate
.OrderByDescending(t => t.Date)
.FirstOrDefault(lt => lt.SomeValue == value)
select new {p, o}
Everything compiles and LINQ isn't complaining, but the result is wrong.
The generated SQL is an OUTER APPLY with a TOP 1, but there is no 'ORDER BY'.
I also tried this:
from p in db.SomeTable
select new {
p,
o = db.SomeTableWithDate
.OrderByDescending(t => t.Date)
.FirstOrDefault(lt => lt.SomeValue == value)
}
But I get the same result. (I prefer 'let' because then I can use variables from the previous 'let' query)
So here is my question: how can i make LINQ do a real subquery with orderby?
I want to get the latest date from a linked table
Solution
The answer from boran solved it. I just had to do a seperate where first.
from p in db.SomeTable
let o = db.SomeTableWithDate
.Where(lt => lt.SomeValue == value)
.OrderByDescending(t => t.Date)
.FirstOrDefault()
select new {p, o}
from p in db.SomeTable
let o = db.SomeTableWithDate.Where(lt => lt.SomeValue == value)
.OrderByDescending(t => t.Date)
.FirstOrDefault()
select new {p, o}
Because you order after filtering, this query will probably have better performance too.
I was asked to produce a report that is driven by a fairly complex SQL query against a SQL Server database. Since the site of the report was already using Entity Framework 4.1, I thought I would attempt to write the query using EF and LINQ:
var q = from r in ctx.Responses
.Where(x => ctx.Responses.Where(u => u.UserId == x.UserId).Count() >= VALID_RESPONSES)
.GroupBy(x => new { x.User.AwardCity, x.Category.Label, x.ResponseText })
orderby r.FirstOrDefault().User.AwardCity, r.FirstOrDefault().Category.Label, r.Count() descending
select new
{
City = r.FirstOrDefault().User.AwardCity,
Category = r.FirstOrDefault().Category.Label,
Response = r.FirstOrDefault().ResponseText,
Votes = r.Count()
};
This query tallies votes, but only from users who have submitted a certain number of required minimum votes.
This approach was a complete disaster from a performance perspective, so we switched to ADO.NET and the query ran very quickly. I did look at the LINQ generated SQL using the SQL Profiler, and although it looked atrocious as usual I didn't see any clues as to how to optimize the LINQ statement to make it more efficient.
Here's the straight TSQL version:
WITH ValidUsers(UserId)
AS
(
SELECT UserId
FROM Responses
GROUP BY UserId
HAVING COUNT(*) >= 103
)
SELECT d.AwardCity
, c.Label
, r.ResponseText
, COUNT(*) AS Votes
FROM ValidUsers u
JOIN Responses r ON r.UserId = u.UserId
JOIN Categories c ON r.CategoryId = c.CategoryId
JOIN Demographics d ON r.UserId = d.Id
GROUP BY d.AwardCity, c.Label, r.ResponseText
ORDER BY d.AwardCity, s.SectionName, COUNT(*) DESC
What I'm wondering is: is this query just too complex for EF and LINQ to handle efficiently or have I missed a trick?
Using a let to reduce the number of r.First()'s will probably improve performance. It's probably not enough yet.
var q = from r in ctx.Responses
.Where()
.GroupBy()
let response = r.First()
orderby response.User.AwardCity, response.Category.Label, r.Count() descending
select new
{
City = response.User.AwardCity,
Category = response.Category.Label,
Response = response.ResponseText,
Votes = r.Count()
};
Maybe this change improve the performance, removing the resulting nested sql select in the where clause
First get the votes of each user and put them in a Dictionary
var userVotes = ctx.Responses.GroupBy(x => x.UserId )
.ToDictionary(a => a.Key.UserId, b => b.Count());
var cityQuery = ctx.Responses.ToList().Where(x => userVotes[x.UserId] >= VALID_RESPONSES)
.GroupBy(x => new { x.User.AwardCity, x.Category.Label, x.ResponseText })
.Select(r => new
{
City = r.First().User.AwardCity,
Category = r.First().Category.Label,
Response = r.First().ResponseText,
Votes = r.Count()
})
.OrderByDescending(r => r.City, r.Category, r.Votes());
i have 4 table in SQL: DocumentType,ClearanceDocument,Request, RequestDocument.
i want when page load and user select one request, show all Document Based on clearanceType in RequestTable and check in RequestDocument and when exist set is_exist=true
I have written this query with SqlServer Query Editor for get result this Scenario but i can't convert this Query to Linq
select *,
is_Orginal=
(select is_orginal from CLEARANCE_REQUEST_DOCUMENT
where
DOCUMENT_ID=a.DOCUMENT_ID and REQUEST_ID=3)
from
DOCUMENT_TYPES a
where
DOCUMENT_ID in
(select DOCUMENT_ID from CLEARANCE_DOCUMENTS dt
where
dt.CLEARANCE_ID=
(SELECT R.CLEARANCE_TYPE FROM CLEARANCE_REQUEST R
WHERE
R.REQUEST_ID=3))
i write this Query in linq but not work
var list = (from r in context.CLEARANCE_REQUEST
where r.REQUEST_ID == 3
join cd in context.CLEARANCE_DOCUMENTS on r.CLEARANCE_TYPE equals cd.CLEARANCE_ID
join dt in context.DOCUMENT_TYPES on cd.DOCUMENT_ID equals dt.DOCUMENT_ID into outer
from t in outer.DefaultIfEmpty()
select new
{
r.REQUEST_ID,
cd.CLEARANCE_ID,
t.DOCUMENT_ID,
t.DOCUMENT_NAME,
is_set=(from b in context.CLEARANCE_REQUEST_DOCUMENT where
b.REQUEST_ID==r.REQUEST_ID && b.DOCUMENT_ID==t.DOCUMENT_ID
select new{b.IS_ORGINAL})
}
).ToList();
I want convert this Query to LINQ. Please help me. Thanks.
There is no need to manually join objects returned from an Entity Framework context.
See Why use LINQ Join on a simple one-many relationship?
If you use the framework as intended your job will be much easier.
var result = var clearanceTypes = context.CLEARANCE_REQUEST
.Single(r => r.REQUEST_ID == 3)
.CLEARANCE_DOCUMENTS
.SelectMany(dt => dt.DOCUMENT_TYPES)
.Select(a => new
{
DocumentType = a,
IsOriginal = a.CLEARANCE_REQUEST_DOCUMENT.is_original
});
Since your query won't be executed untill you iterate over the data, you can split your query in several subqueries to help you obtain the results like this:
var clearanceIds = context.CLEARANCE_REQUEST
.Where(r => r.REQUEST_ID == 3)
.Select(r => r.CLEARANCE_TYPE);
var documentIds = context.CLEARANCE_DOCUMENTS
.Where(dt => clearanceIds.Contains(dt.CLEARANCE_ID))
.Select(dt => dt.DOCUMENT_ID);
var result = context.DOCUMENT_TYPES
.Where(a => documentIds.Contains(a.DOCUMENT_ID))
.Select(a => new
{
// Populate properties here
IsOriginal = context.CLEARANCE_REQUEST_DOCUMENT
.Single(item => item.DOCUMENT_ID == a.DOCUMENT_ID &&
item.REQUEST_ID == 3)
.IS_ORIGINAL
})
.ToList();
var users = from user in st.Users
where user.UDID == cr.User.Udid
select user;
var cityIds from city in users.First().Cities
select city.ID;
DoSomethingWith(cityIds);
It started as this query:
select CityID from UserCities inner join User on User.ID=UserID where User.UDID=#UDID;
I can't seem to get the join syntax right with Linq-to-Entities
Using query expressions isn't really helping you here, and you wouldn't need two of them anywehere. Here's a direct translation:
var cityIds = st.Users
.Where(user => user.UDID == cr.User.Udid)
.First()
.Cities
.Select(city => city.ID);
Now use the fact that First can take a predicate, and you can remove the Where:
var cityIds = st.Users
.First(user => user.UDID == cr.User.Udid)
.Cities
.Select(city => city.ID);
I figured out what I wanted to achieve.
var cityIds = from city in st.Users.First(x => x.UDID == cr.User.Udid).Cities
select city.ID