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Linq Join to List

I have a list as follows:
List<int> loc = new List<int>();
which I populate.
Note that the list stores int values.
I like to join this list to a db table as follow.
What I need to do is something like:
var result = (from pc in db.loc_details
join l in loc
on pc.locid = loc
select pc).ToList();
I get an error obviously: Cannot implicitly convert type 'System.Connection.Generics.List to 'int'.
What is the best approach to do this?

You're trying to join a single int to the entire list.
Try
var result = (from pc in db.loc_details
join l in loc
on pc.locid equals l
select pc).ToList();
although that will gve you a different error if you are using EF since it can't translate a join to an in-memory list to SQL. If that is the case, you can use Contains which gets translated to an IN clause:
var result = (from pc in db.loc_details
where loc.Contains(pc.locid)
select pc).ToList();

You wrote:
List<int> loc = new List<int>();
var result = (from pc in db.loc_details
join l in loc
on pc.locid = loc
select pc);
Answer yourself: what is the type of pc.LocId? And what is the type of loc?
Now look at your code:
on pc.locid = loc
by the way, shouldn't the = be equals or at least ==?

Have a Query want it in LINQ(Inner Join)

I'm having problem translating a query to LINQ in C# this is my query
select PDF.Name,PDF.Name
from PDF inner join PC
on PDF.Id=PC.Ref_PDF
having pc.Ref_Customer=_id
you should know that _id is something that i send to my method so I can find something with it
so far I did this which I don't think would work(cuase lot's of errors poped up)
Invalid expression term 'select'
and
Expected contextual keyword 'equals'
both at end of here join p in Context.PDFs on c.Ref_PDF
internal List<EF_Model.PDF> Customers_File(int _id)
{
using (var Context = new EF_Model.CoolerEntities())
{
var q = from c in Context.PCs
where c.Ref_Customer == _id
join p in Context.PDFs on c.Ref_PDF
select new { c.PDF.Id, c.PDF.Name, c.PDF.File };
return q;
}
}
How can we make it into a linq statement?

Fix the syntax for the query
List<EF_Model.PDF> Customers_File(int _id) {
using (var Context = new EF_Model.CoolerEntities()) {
var q = from c in Context.PCs
join p in Context.PDFs on c.Ref_PDF equals p.Id
where c.Ref_Customer == _id
select new EF_Model.PDF { Id = c.PDF.Id, Name = c.PDF.Name, File = c.PDF.File };
return q.ToList();
}
}
and the method expects to return a list so use the ToList() on the query when returning from the method.
UPDATE:
If the intention was just to return the PDF model then no need to create the anonymous object just return c.PDF
List<EF_Model.PDF> Customers_File(int _id) {
using (var Context = new EF_Model.CoolerEntities()) {
var q = from c in Context.PCs
join p in Context.PDFs on c.Ref_PDF equals p.Id
where c.Ref_Customer == _id
select c.PDF;
return q.ToList();
}
}

This should do the job for you
from pc in context.PCs where pc.Ref_Customer == _id
join p in context.PDFs on pc.Ref_PDF equals p.Ref_PDF
select new {pc.PDF.Id, pc.PDF.Name, pc.PDF.File }
Probably when you said errors, I assume you saw synactical errors

If you set up a navigation property, the query is:
var q =
from pc in Context.PCs
where pc.Ref_Customer == _id
from pdf in pc.PDFs
select pdf;
If you don't:
var q =
from pc in Context.PCs
where pc.Ref_Customer == _id
join pdf in Context.PDFs on pc.Ref_PDF equals pdf.Id
select pdf;
The main thing to know about the join syntax, it has the form
" join (a) in (b) on (c) equals (d) "
(a): the new range variable for a member of (b)
(b): the source of items you are joining to - the right side of the join.
(c): an expression in which the item from the left side of the join is in scope.
(d): an expression in which the item from the right side of the join is in scope - (a).

Convert My Code SQL to LINQ?

Kindly convert my SQL to LINQ. I'm really desperate. It includes multiple filtering (2).
SELECT dbo.EmployeeAccess.EmpNo,
dbo.View_SystemAdminMembers.LNameByFName,
dbo.View_SystemAdminMembers.GroupName,
dbo.View_SystemAdminMembers.Role,
dbo.View_SystemAdminMembers.Active,
dbo.View_SystemAdminMembers.EmpNo AS Expr4,
dbo.View_SystemAdminMembers.RoleID
FROM dbo.EmployeeAccess
INNER JOIN dbo.View_SystemAdminMembers
ON dbo.EmployeeAccess.GroupID = dbo.View_SystemAdminMembers.GroupID
WHERE (dbo.EmployeeAccess.EmpNo = '50')
Thank you so much in advance.

Please try with the below code snippet.
var result =from e in context.EmployeeAccess
join v in context.View_SystemAdminMembers on e.GroupID equals v.GroupID
Where e.EmpNo == 50
select new { e.EmpNo,v.LNameByFName,v.GroupName,v.Role,v.Active,a.RoleID,v.EmpNo as VEmpNo };
Note : context is your DB Context object.
Let me know if any concern.

var results = (from ea in DbContext.EmployeeAccess
join sam in DbContext.View_SystemAdminMembers on ea.GroupId equals sam.GroupId
where ea.EmpNo = '50'
select new {
ea.EmpNo,
sam.LNameByFName,
sam.GroupName,
sam.Role,
sam.Active,
Expr4 = sam.EmpNo,
sam.RoleID
};
You didnt mention what your database context was, you'll have to fill that in yourself.

var res = (from x in ctx.EmployeeAccess
join y in ctx.View_SystemAdminMembers on x.GroupId equals y.groupId
where x.EmpNo = '50'
select new
{
x.EmpNo,
y.LNameByFName,
y.GroupName,
y.Role,
y.Active,
Expr4 = y.EmpNo,
y.RoleID
});
Note: do NOT use = when joining, but equals.

LINQ using dictionary in where clause

er have the following query in linq...
Whenever I try to run it I get a No comparison operator for type System.Int[] exception.
It's got something to do with the dictionary I am sure, but I don't understand why this isn't valid and was wondering if someone could explain?
// As requested... not sure it will help though.
var per = (
from p in OtherContext.tblPeriod
where activeContractList.Select(c => c.DomainSetExtensionCode).Contains(p.DomainSetExtensionCode)
select p).ToArray();
var com = (
from c in MyContext.tblService
join sce in MyContext.tblServiceExtension
on c.ServiceExtensionCode equals sce.ServiceExtensionCode
join sc in MyContext.tblServiceContract
on sce.ServiceContractCode equals sc.ContractCode
group sc by c.Period into comG
select new
{
PeriodNumber = comG.Key,
Group = comG,
}).ToArray();
var code =
(from c in com
join p in per on c.PeriodNumber equals p.PeriodNumber
select new
{
p.Code,
c.Group
}).ToArray();
var payDictionary = new Dictionary<int, int[]>();
// This is another linq query that returns an anonymous type with
// two properties, and int and an array.
code.ForEach(c => payDictionary.Add(c.Code, c.Group.Select(g => g.Code).ToArray()));
// MyContext is a LINQ to SQL DataContext
var stuff = (
from
p in MyContext.tblPaySomething
join cae in MyContext.tblSomethingElse
on p.PaymentCode equals cae.PaymentCode
join ca in MyContext.tblAnotherThing
on cae.SomeCode equals ca.SomeCode
where
// ca.ContractCode.Value in an int?, that should always have a value.
payDictionary[p.Code].Contains(ca.ContractCode.Value)
select new
{
p.Code,
p.ExtensionCode,
p.IsFlagged,
p.Narrative,
p.PayCode,
ca.BookCode,
cae.Status
}).ToList();

You won't be able to do this with a dictionary. The alternative is to join the three linq queries into one. You can do this with minimal impact to your code by not materializing the queries with ToArray. This will leave com and code as IQueryable<T> and allow for you compose other queries with them.
You will also need to use a group rather than constructing a dictionary. Something like this should work:
var per = (
from p in OtherContext.tblPeriod
where activeContractList.Select(c => c.DomainSetExtensionCode).Contains(p.DomainSetExtensionCode)
select p.PeriodNumber).ToArray(); // Leave this ToArray because it's materialized from OtherContext
var com =
from c in MyContext.tblService
join sce in MyContext.tblServiceExtension on c.ServiceExtensionCode equals sce.ServiceExtensionCode
join sc in MyContext.tblServiceContract on sce.ServiceContractCode equals sc.ContractCode
group sc by c.Period into comG
select new
{
PeriodNumber = comG.Key,
Group = comG,
}; // no ToArray
var code =
from c in com
where per.Contains(c.PeriodNumber) // have to change this line because per comes from OtherContext
select new
{
Code = c.PeriodNumber,
c.Group
}; // no ToArray
var results =
(from p in MyContext.tblPaySomething
join cae in MyContext.tblSomethingElse on p.PaymentCode equals cae.PaymentCode
join ca in MyContext.tblAnothThing on cae.SomeCode equals ca.SomeCode
join cg in MyContext.Codes.GroupBy(c => c.Code, c => c.Code) on cg.Key equals p.Code
where cg.Contains(ca.ContractCode.Value)
select new
{
p.ContractPeriodCode,
p.DomainSetExtensionCode,
p.IsFlagged,
p.Narrative,
p.PaymentCode,
ca.BookingCode,
cae.Status
})
.ToList();
Side Note: I also suggest using navigation properties where possible instead of joins. It makes it much easier to read and understand how objects are related and create complex queries.

Entity Framework query error?

I'm getting this error:
The entity or complex type 'Model.Members' cannot be constructed in a LINQ to Entities query.
with my code:
public List<Members> getTeamMembers(String tem_reference)
{
var query = from c in cecbContext.Projects
join b in cecbContext.TeamMembers on c.proj_team equals b.team_reference
join d in cecbContext.Members on b.mem_reference equals d.mem_reference
where c.proj_reference == tem_reference
select new Members
{
mem_reference = d.mem_reference
};
return query.ToList<Members>();
}

I believe you're running into problems because you're trying to project a mapped entity, and this answer would tell you more: https://stackoverflow.com/a/5325861/2208058
This is what I think might work for you:
var query = from c in cecbContext.Projects
join b in cecbContext.TeamMembers on c.proj_team equals b.team_reference
join d in cecbContext.Members on b.mem_reference equals d.mem_reference
where c.proj_reference == tem_reference
select d.mem_reference;
return query.Select(ref => new Members { mem_reference = d.mem_reference }).ToList();