select ForumCategories.ID , ForumCategories.Title , ForumCategories.DateCreated,
CO = ( select COUNT(*) from ForumSubCategories where ForumSubCategories.CategoryID_FK = ForumCategories.ID)
from ForumCategories
var q = from fc in Context.ForumCategories
select new
{
Id = fc.ID,
Title = fc.Title,
DateCreated = fc.DateCreated
CO = fc.ForumSubCategories.Count()
};
return q;
The "join" (subquery) is implicit; it's defined in the relationship between ForumCategories and ForumSubCategories in your model. Using this syntax, the call to Count() will be done on the DB server.
Related
Is it possible to do orderby expression using linq query expression based on dynamic string parameter? because the query i have is producing weird SQL query
my linq:
var product = from prod in _context.Products
join cat in _context.Categories on prod.CategoryId equals cat.CategoryId
join sup in _context.Suppliers on prod.SupplierId equals sup.SupplierId
orderby sortParam
select new ProductViewModel
{
ProductName = prod.ProductName,
ProductId = prod.ProductId,
QuantityPerUnit = prod.QuantityPerUnit,
ReorderLevel = prod.ReorderLevel,
UnitsOnOrder = prod.UnitsOnOrder,
UnitPrice = prod.UnitPrice,
UnitsInStock = prod.UnitsInStock,
Discontinued = prod.Discontinued,
Category = cat.CategoryName,
Supplier = sup.CompanyName,
CategoryId = cat.CategoryId,
SupplierId = sup.SupplierId
};
where var sortParam = "prod.ProductName"
The code above produces weird sql where order by sortParam is being converted to (SELECT 1). Full query catched by sql profiler below:
exec sp_executesql N'SELECT [prod].[ProductName], [prod].[ProductID], [prod].[QuantityPerUnit], [prod].[ReorderLevel], [prod].[UnitsOnOrder], [prod].[UnitPrice], [prod].[UnitsInStock], [prod].[Discontinued], [cat].[CategoryName] AS [Category], [sup].[CompanyName] AS [Supplier], [cat].[CategoryID], [sup].[SupplierID]
FROM [Products] AS [prod]
INNER JOIN [Categories] AS [cat] ON [prod].[CategoryID] = [cat].[CategoryID]
INNER JOIN [Suppliers] AS [sup] ON [prod].[SupplierID] = [sup].[SupplierID]
ORDER BY (SELECT 1)
OFFSET #__p_1 ROWS FETCH NEXT #__p_2 ROWS ONLY',N'#__p_1 int,#__p_2 int',#__p_1=0,#__p_2=10
I'm seeing a lot of people doing linq order by using dynamic parameter but all of them use lambda not query expression, please enlighten me
As was already mentioned, you are passing a string value instead of an expression that reflects the column name. There are options for what you want however, see for example here.
I have a linq query that works fine when I join two tables, but when I include another table, it does not return data. Please help me figure out what I am doing wrong.
First Linq returns data:
var q = (from c in _context.Complaint
join cl in _context.Checklist on c.COMP_ID equals cl.COMP_ID into clleft
from cls in clleft.DefaultIfEmpty()
orderby c.timestamp descending
select new
{
FileNum = c.FileNum
}).AsQueryable().Distinct();
return q;
When I add this table, no data returns
var q = (from c in _context.Complaint
join cl in _context.Checklist on c.COMP_ID equals cl.COMP_ID into clleft
from cls in clleft.DefaultIfEmpty()
join oim in _context.OIM_EMPLOYEE on cls.MonitorEnteredEmpID equals oim.EmpID into oimleft
from oims in oimleft.DefaultIfEmpty()
orderby c.timestamp descending
select new
{FileNum = c.FileNum
}).AsQueryable().Distinct();
return q;
I am trying to flatten out my webapi EF using a DTO and linq but not quite sure how to do it. My end goal is to say, I want to return ALL four accounts where USERNAME = x.
In this example there is 1 username with access to 1 client, and that 1 client has 4 accounts.
How can I make the result come back with 4 entries, 1 for each account?
Here is what I have so far...
var x2 = from b in db.AspNetUsers
where b.UserName == username
select new AspNetUserDetailDTO()
{
UserName = b.UserName,
Email = b.Email,
Mapping_UserClient = b.Mapping_UserClient
//ClientName = b.Mapping_UserClient.SelectMany<Mapping_UserClient>(x => x.ClientID)
//Mapping_UserClient = b.Mapping_UserClient
};
below is my sql diagram.
so I tried writing a plain sql query to return a basic result of what I am looking for... now I do not know how to do this in LINQ
SELECT
dbo.Clients.ClientName
,dbo.Mapping_UserClient.ClientID
,*
FROM [xxx].[dbo].[AspNetUsers]
inner join dbo.Mapping_UserClient on dbo.Mapping_UserClient.AspNetUsersID = dbo.AspNetUsers.Id
inner join dbo.Clients on dbo.Clients.ClientID = dbo.Mapping_UserClient.ClientID
inner join dbo.Mapping_ClientAccount on dbo.Mapping_ClientAccount.ClientID = dbo.Clients.ClientID
inner join dbo.Accounts on dbo.Accounts.AccountID = dbo.Mapping_ClientAccount.AccountID
where Email = 'dddd'
Translating your query above, you would get something like this in Linq:
var query = (from acc in db.Accounts
join mca in db.Mapping_ClientAccount
on acc.AccountId equals mca.ClientID
join cli in db.Clients
on mca.ClientID equals cli.ClientID
join muc in db.Mapping_UserClient
on cli.ClientID equals muc.ClientID
join anu in db.AspNetUsers
on muc.AspNetUsersID equals anu.Id
where anu.UserName == username
select new AspNetUserDetailsDTO()
{
ClientName = cli.ClientName,
ClientID = cli.ClientID
}).ToList();
this question is in relation to my previous question: Linq2Entity Getting Values from reference Table
Now i have the problem that i want to add a new entry in Table B. I tried something like this:
ObjectQuery<A> aTable = dbConnection.A;
ObjectQuery<B> bTable = dbConnection.B;
var data = from d in aTable //Reference dataset in Table A
where d.ID == myID
select d;
B bData = new B()
{
ID = GetNewID(),
Text = text,
A = data.First()
};
dbConnection.AddToB(bData);
but this "A = d.First()" does now work... Any ideas? Thx!
I have several linked tables (entities). I'm trying to get the entities using the following linq:
ObjectQuery<Location> locations = context.Location;
ObjectQuery<ProductPrice> productPrice = context.ProductPrice;
ObjectQuery<Product> products = context.Product;
IQueryable<ProductPrice> res1 = from pp in productPrice
join loc in locations
on pp.Location equals loc
join prod in products
on pp.Product equals prod
where prod.Title.ToLower().IndexOf(Word.ToLower()) > -1
select pp;
This query returns 2 records, ProductPrice objects that have linked object Location and Product but they are null and I cannot understand why. If I try to fill them in the linq as below:
res =
from pp in productPrice
join loc in locations
on pp.Location equals loc
join prod in products
on pp.Product equals prod
where prod.Title.ToLower().IndexOf(Word.ToLower()) > -1
select new ProductPrice
{
ProductPriceId = pp.ProductPriceId,
Product = prod
};
I have the exception "The entity or complex type 'PBExplorerData.ProductPrice' cannot be constructed in a LINQ to Entities query"
Could someone please explain me what happens and what I need to do?
Thanks
The answer to your first question the Product and Location are null because you need to add an Include("") to your query.
IQueryable<ProductPrice> res1 = from pp in
productPrice.Include("Location").Include("Product")
join loc in locations
on pp.Location equals loc
join prod in products
on pp.Product equals prod
where prod.Title.ToLower().IndexOf(Word.ToLower()) > -1
select pp;
The second issue is EF is trying to push down your query and ProductPrice (is not an entity) so it can not. If you want to do this convert it to an anonymous type so just do
select new
{
ProductPriceId = pp.ProductPriceId,
Product = prod
};
And then do
res.ToList().ConvertAll(x=new ProductPrice () {
ProductPriceId = x.ProductPriceId ,
Product = x.Product
});
Or you could do it other ways, by selecting the entity you want, and just populating manual.