Query:
select emp.empname as Name, dep.depname as Department
from Employee as emp
inner join Department as dep on emp.depid=dep.depid
where emp.id='2'
How can I change this to linq to sql?
var id = 2;
var qry = from e in db.Employees
where e.Id == id
select new {
Name = e.EmpName,
Department = e.Department.DepName
};
(assumes the parent-association between employee and department is defined in the DBML)
and if you expect exactly one such:
var record = qry.Single();
Console.WriteLine(record.Name);
Console.WriteLine(record.Department);
Approximately:
from e in dc.Employee
join d in dc.Department on e.depid equals d.depid
where e.id == '2'
select new
{
Name = e.empname,
Department = d.depname
}
This is why LINQ is so great: there is no reason to even join with the Departments table to get it to work:
from employee in db.Employees
where employee.id == 2
select new
{
Name = employee.empname,
Department = employee.Department.depname
};
Related
I have 3 table User,HumanCustomer,CompanyCustomer
I want to join between tables with LINQ but my query is not working and its returning null
Query:
var query = (from users in _ctx.Users
join hCustomer in _ctx.HumanCustomers on users.Id equals hCustomer.UserId
join cCustomer in _ctx.CompanyCustomers on users.Id equals cCustomer.UserId
select new
{
users.Id,
users.Mobile,
hCustomer.LastName,
hCustomer.Name,
cCustomer.CompanyName
});
foreach (var item in query)
{
AllCustomerViewModel allCustomer = new AllCustomerViewModel();
if (item.Name != null)
{
allCustomer.UserId = item.Id;
allCustomer.FullName = item.Name + item.LastName;
allCustomer.Mobile = item.Mobile;
Customer.Add(allCustomer);
}
}
The code does not enter foreach
I think the problem is using UserId twice because when I delete
join cCustomer in _ctx.CompanyCustomers on users.Id equals cCustomer.UserId
the query runs correctly.
Perhaps your issue is the dynamic variable you are attempting to iterate over.
You could try:
foreach (dynamic item in query)
Alternatively, you write the class to hold the values you are selecting out by updating the beginning of your query to:
var query = (from users in _ctx.Users
join hCustomer in _ctx.HumanCustomers on users.Id equals hCustomer.UserId
join cCustomer in _ctx.CompanyCustomers on users.Id equals cCustomer.UserId
select new MyClass
{
Id = users.Id,
Mobile = users.Mobile,
LastName = hCustomer.LastName,
Name = hCustomer.Name,
CompanyName = cCustomer.CompanyName
});
you can try this way..
var query = (from users in _ctx.Users
join hCustomer in _ctx.HumanCustomers on users.Id equals hCustomer.UserId
join cCustomer in _ctx.CompanyCustomers on users.Id equals cCustomer.UserId
select new
{
Id = users.Id,
Mobile = users.Mobile,
LastName = hCustomer.LastName,
Name = hCustomer.Name,
CompanyName = (cCustomer == null ? "" : cCustomer .CompanyName)
});
I'm having difficulty converting this sql query to a linq query. I'm trying to select all my orders with the order details attached to that order. In sql the query is correct. When I write it in linq is when everything goes haywire. Here is my code:
var result = from order in orders
join orderDetail in orderDetails
on order.OrderID equals orderDetail.OrderID
select new OrderVm
{
OrderId = order.OrderID,
OrderDetails = order.Order_Details.Select(x =>
new OrderDetailVm
{
OrderId = orderDetail.OrderID,
UnitPrice = orderDetail.UnitPrice,
Quantity = orderDetail.Quantity,
ProductId = orderDetail.ProductID
})
};
return result.ToList();
that produces this result
but in sql if I write
select
o.OrderID,
o.CustomerID,
od.UnitPrice,
od.Quantity,
od.productid,
p.ProductName
from Orders o
inner join [Order Details] od
on o.OrderID = od.OrderID
inner join Products p
on p.ProductID = od.ProductID
where o.OrderID = 10248
my expected out come is
It looks like from the way that you are using Order_Details in the nested object that the join already exists and that the join you are using is redundant.
var result = from order in orders
select new OrderVm
{
OrderId = order.OrderID,
OrderDetails = order.Order_Details.Select(x =>
new OrderDetailVm
{
OrderId = x.OrderID,
UnitPrice = x.UnitPrice,
Quantity = x.Quantity,
ProductId = x.ProductID
})
};
I am trying to convert below query in linq
select ta.id, ta.name, min(tb.id) from tableA ta
left join tableB tb on tb.fkid=ta.id
group by ta.id, ta.name
I tried below
var query = (from tableA in tableARepository.AsQueryable()
join tableB in tableBRepository.AsQueryable() on
tableA.Id equals tableB.fkid
group grp by new {tableA.Id, tableA.Name } into groupedCol
select new
{
Id = groupedCol.Key.Id,
Name = groupedCol.Key.Name,
fkId = grouppedCol.Min // cant get column fkid from tableB
}
);
I am not able to get Min of column fkid of tableB
What is missing here or how can i fix this?
You should be able to get the results that you are looking for without using Join or GroupBy:
var restrictTo = new[] {1, 2};
var query = tableARepository.AsQueryable()
// I want to add where clause like tableA.Id in (1,2)
.Where(a => restrictTo.Contains(a.Id))
.Select(a => new {
Id = a.Id
, Name = a.Name
, FkId = tableBRepository.AsQueryable().Min(b => b.fkid=a.id)
});
I think you are looking for GroupJoin
from tableA in tableARepository.AsQueryable()
join tableB in tableBRepository.AsQueryable() on
tableA.Id equals tableB.fkid into tb
select new
{
Id = tableA.Id,
Name = tableA.Name,
fkId = tb.Min(x => x.id)
}
The SQL would be something like
select GeneralData.id, GeneralData.name, GeneralData.last_name, Student.id
from GeneralData Inner JOIN Student ON Student.id=GeneralData.id
GeneralData is dt1
Student is dt2
what I want to get is dt3
have some proposals?
var query =
from s in db.Student
from g in db.GeneralData
where s.id == g.id
select new
{
g.id,
g.name,
g.last_name
};
var query = from data in dc.GeneralData
join stud in dc.Students in data.id equals stud.id
select new
{
data.id, data.Name, data.LastName, stud.id
};
Something like this:
var result= (
from general in db.GeneralData
join student in db.Student
on general.id=student.id
select new
{
general.id,
general.name,
general.last_name,
studentId=student.id
}
);
where db is the linq data context
As a method chain:
dt2.Where(s=>s.id == 1)
.Select(s=> new {Stud = s, Data= dt1.Where(g=>g.id == s.id)}).First()
.Select(q=> new {q.Stud.id, q.Data.name, q.data.last_name}).FirstOrDefault();
I have three tables, Professors, ProfessorStudent, Student.
I want all Professors + How many Students each Professor have.
I can do this:
context.ProfessorSet.Include("Student")
context.ProfessorSet.Include("Student").ToList() will read all three tables.
But i dont wanna get Student table, I want that Linq just get "Professor Table"+ "Count(*) ProfessorStudent Group By StudentId".
Its possible?
I do using this:
var c = from tag in contexto.ProfessorSet
select new
{
Tag = tag,
Count = tag.Student.Count
};
But generate this SQL:
SELECT
C.Id,
C.Nome,
C.C1
FROM
(SELECT
A.Id,
A.Nome,
(SELECT
COUNT(0)
FROM ProfessorStudant AS B
WHERE A.Id = B.ProfessorId
) AS [C1]
FROM Professor AS A)
I want this:
Select A.Id, Count(0) from Professor A
inner join ProfessorStudent B on A.Id = B.ProfessorId
Group By A.Id
from p in context.ProfessorSet
from s in p.Student
group s by s.StudentId into g
select new
{
Professor = p,
StudentCounts = from sc in g
select new
{
StudentId = sc.Key,
Count = sc.Group.Count()
}
}