I'm writing a LINQ to SQL statement, and I'm after the standard syntax for a normal inner join with an ON clause in C#.
How do you represent the following in LINQ to SQL:
select DealerContact.*
from Dealer
inner join DealerContact on Dealer.DealerID = DealerContact.DealerID
It goes something like:
from t1 in db.Table1
join t2 in db.Table2 on t1.field equals t2.field
select new { t1.field2, t2.field3}
It would be nice to have sensible names and fields for your tables for a better example. :)
Update
I think for your query this might be more appropriate:
var dealercontacts = from contact in DealerContact
join dealer in Dealer on contact.DealerId equals dealer.ID
select contact;
Since you are looking for the contacts, not the dealers.
And because I prefer the expression chain syntax, here is how you do it with that:
var dealerContracts = DealerContact.Join(Dealer,
contact => contact.DealerId,
dealer => dealer.DealerId,
(contact, dealer) => contact);
To extend the expression chain syntax answer by Clever Human:
If you wanted to do things (like filter or select) on fields from both tables being joined together -- instead on just one of those two tables -- you could create a new object in the lambda expression of the final parameter to the Join method incorporating both of those tables, for example:
var dealerInfo = DealerContact.Join(Dealer,
dc => dc.DealerId,
d => d.DealerId,
(dc, d) => new { DealerContact = dc, Dealer = d })
.Where(dc_d => dc_d.Dealer.FirstName == "Glenn"
&& dc_d.DealerContact.City == "Chicago")
.Select(dc_d => new {
dc_d.Dealer.DealerID,
dc_d.Dealer.FirstName,
dc_d.Dealer.LastName,
dc_d.DealerContact.City,
dc_d.DealerContact.State });
The interesting part is the lambda expression in line 4 of that example:
(dc, d) => new { DealerContact = dc, Dealer = d }
...where we construct a new anonymous-type object which has as properties the DealerContact and Dealer records, along with all of their fields.
We can then use fields from those records as we filter and select the results, as demonstrated by the remainder of the example, which uses dc_d as a name for the anonymous object we built which has both the DealerContact and Dealer records as its properties.
var results = from c in db.Companies
join cn in db.Countries on c.CountryID equals cn.ID
join ct in db.Cities on c.CityID equals ct.ID
join sect in db.Sectors on c.SectorID equals sect.ID
where (c.CountryID == cn.ID) && (c.CityID == ct.ID) && (c.SectorID == company.SectorID) && (company.SectorID == sect.ID)
select new { country = cn.Name, city = ct.Name, c.ID, c.Name, c.Address1, c.Address2, c.Address3, c.CountryID, c.CityID, c.Region, c.PostCode, c.Telephone, c.Website, c.SectorID, Status = (ContactStatus)c.StatusID, sector = sect.Name };
return results.ToList();
You create a foreign key, and LINQ-to-SQL creates navigation properties for you. Each Dealer will then have a collection of DealerContacts which you can select, filter, and manipulate.
from contact in dealer.DealerContacts select contact
or
context.Dealers.Select(d => d.DealerContacts)
If you're not using navigation properties, you're missing out one of the main benefits on LINQ-to-SQL - the part that maps the object graph.
Use Linq Join operator:
var q = from d in Dealer
join dc in DealerConact on d.DealerID equals dc.DealerID
select dc;
basically LINQ join operator provides no benefit for SQL. I.e. the following query
var r = from dealer in db.Dealers
from contact in db.DealerContact
where dealer.DealerID == contact.DealerID
select dealerContact;
will result in INNER JOIN in SQL
join is useful for IEnumerable<> because it is more efficient:
from contact in db.DealerContact
clause would be re-executed for every dealer
But for IQueryable<> it is not the case. Also join is less flexible.
Actually, often it is better not to join, in linq that is. When there are navigation properties a very succinct way to write your linq statement is:
from dealer in db.Dealers
from contact in dealer.DealerContacts
select new { whatever you need from dealer or contact }
It translates to a where clause:
SELECT <columns>
FROM Dealer, DealerContact
WHERE Dealer.DealerID = DealerContact.DealerID
Inner join two tables in linq C#
var result = from q1 in table1
join q2 in table2
on q1.Customer_Id equals q2.Customer_Id
select new { q1.Name, q1.Mobile, q2.Purchase, q2.Dates }
Use LINQ joins to perform Inner Join.
var employeeInfo = from emp in db.Employees
join dept in db.Departments
on emp.Eid equals dept.Eid
select new
{
emp.Ename,
dept.Dname,
emp.Elocation
};
Try this :
var data =(from t1 in dataContext.Table1 join
t2 in dataContext.Table2 on
t1.field equals t2.field
orderby t1.Id select t1).ToList();
OperationDataContext odDataContext = new OperationDataContext();
var studentInfo = from student in odDataContext.STUDENTs
join course in odDataContext.COURSEs
on student.course_id equals course.course_id
select new { student.student_name, student.student_city, course.course_name, course.course_desc };
Where student and course tables have primary key and foreign key relationship
try instead this,
var dealer = from d in Dealer
join dc in DealerContact on d.DealerID equals dc.DealerID
select d;
var Data= (from dealer in Dealer join dealercontact in DealerContact on dealer.ID equals dealercontact.DealerID
select new{
dealer.Id,
dealercontact.ContactName
}).ToList();
var data=(from t in db.your tableName(t1)
join s in db.yourothertablename(t2) on t1.fieldname equals t2.feldname
(where condtion)).tolist();
var list = (from u in db.Users join c in db.Customers on u.CustomerId equals c.CustomerId where u.Username == username
select new {u.UserId, u.CustomerId, u.ClientId, u.RoleId, u.Username, u.Email, u.Password, u.Salt, u.Hint1, u.Hint2, u.Hint3, u.Locked, u.Active,c.ProfilePic}).First();
Write table names you want, and initialize the select to get the result of fields.
from d1 in DealerContrac join d2 in DealerContrac on d1.dealearid equals d2.dealerid select new {dealercontract.*}
One Best example
Table Names : TBL_Emp and TBL_Dep
var result = from emp in TBL_Emp join dep in TBL_Dep on emp.id=dep.id
select new
{
emp.Name;
emp.Address
dep.Department_Name
}
foreach(char item in result)
{ // to do}
I need to retrieve a list of orders records, and on the same view I have to show for each order:
how many invoices have been issued (InvoiceCount)
the total amount covered by the invoices (Invoiced)
how much has been paid for the issued invoices (Payed)
all on the same grid view.
I think it's a basic view for business management software.
Order > invoices = one-to-many
Payments are related to invoices with a look-up table PaymentsToInvoices
GridView is paged server-side, with a page-size of 50 records.
I've written the following LINQ, that it works fine, but I have some doubt that is well written in terms of performance,
especially if this query is finally translated with a couple of sub-queries, that means 50*2 queries for each request!
var orders = (from o in db.Orders
join c in db.Customers on o.CustomerID equals c.CustomerID
join os in db.OrderStatuses on o.OrderStatusID equals os.OrderStatusID
join ps in db.PaymentStatuses on o.PaymentStatusID equals ps.PaymentStatusID
join ec in db.EntryChannels on o.EntryChannelID equals ec.EntryChannelID
orderby o.InsertDate descending
where o.OrderStatusID == 2
select new
{
o.OrderID,
o.CustomerID,
o.InsertDate,
o.TotalPrice,
o.Notes,
c.FirstName,
c.LastName,
OrderStatus = os.Name,
PaymentStatus = ps.Name,
EntryChannel = ec.Name,
InvoiceCount = (db.InvoiceDetails.Where(i => i.OrderID == o.OrderID).Select(s => s.InvoiceID).Distinct().Count()),
Invoiced = (db.InvoiceDetails.Where(i => i.OrderID == o.OrderID).Select(s => s.TotalPrice).Sum()),
Payed = (from py in db.Payments
join pti in db.PaymentsToInvoices on py.PaymentID equals pti.PaymentID
join inv in db.InvoiceDetails on pti.InvoiceID equals inv.InvoiceID
where inv.OrderID==o.OrderID
select new { py.PaymentID, py.Amount }).Distinct().Select(s=>s.Amount).Sum()
});
What do you think about the last three fields? Can they be improved in some way? Do they result in performance killer sub-queries?
I am using linq to query many to many relationship
I have those tables/entities :
Each order has multiple products and I want to get distinct order with products.
Here is my query:
var query = (from order in db.Order
join orderproduct in db.OrderProduct
on order.orderId equals orderproduct.OrderId
join product in db.Product
on orderproduct.ProductId equals product.productId
select new
{ order.orderId,
order.name,
product.productId,
product.productName,
product.price
}).Distinct().ToList();
This is the result :
I want to get only name "Jane" with 2 products. The result is showed 2 records with same name "Jane".
How to get one record name "jane" and 2 products?
Thanks for your help.
use the following:
var query = (from order in db.Order
join orderproduct in db.OrderProduct
on order.orderId equals orderproduct.OrderId
join product in db.Product
on orderproduct.ProductId equals product.productId
select new {order.orderId,order.name,product.productId,product.productName,product.price}).GroupBy(order=>order.orderId).ToList();
If you want to return a structure containing the customer's name and its ordered products, I recommend to group the products by order.orderName (not order.orderId) and to load the result into a dictionary:
var query = from order in db.Order
join orderproduct in db.OrderProduct on order.orderId equals orderproduct.OrderId
join product in db.Product on orderproduct.ProductId equals product.productId
group product by order.orderName into orderGroup
select orderGroup;
var orderedProductsByName = query.ToDictionary(name => name.Key, products => products.ToList());
Consider the following fictitious scenario:
How would I go about getting a list of all the categories (distinct or otherwise, it doesn't matter) for each customer, even if a customer hasn't ordered any products?
Also assume that we don't have navigation properties, so we'll need to use manual joins.
This is my attempt which uses nesting:
var customerCategories = from c in context.Customers
join o in context.Orders on c.CustomerId equals o.CustomerId into orders
select new
{
CustomerName = c.Name,
Categories = (from o in orders
join p in context.Products on o.ProductId equals p.ProductId
join cat in context.Category on p.CategoryId equals cat.CategoryId
select cat)
};
Is there a different (possibly better way) to achieve the same outcome?
Alternative: Multiple Left (Group) Joins
var customerCategories = from customer in context.Customers
join o in context.Orders on customer.CustomerId equals o.CustomerId into orders
from order in orders.DefaultIfEmpty()
join p in context.Products on order.ProductId equals p.ProductId into products
from product in products.DefaultIfEmpty()
join cat in context.Categories on product.CategoryId equals cat.CategoryId into categories
select new
{
CustomerName = c.Name,
Categories = categories
};
I recreated your table structure and added some data so that I could get a better idea what you were trying to do. I found a couple of ways to accomplish what you want but I'm just going to add this method. I think it's the most concise and I think it's pretty clear.
Code
var summaries = Customers.GroupJoin(Orders,
cst => cst.Id,
ord => ord.CustomerId,
(cst, ord) => new { Customer = cst, Orders = ord.DefaultIfEmpty() })
.SelectMany(c => c.Orders.Select(o => new
{
CustomerId = c.Customer.Id,
CustomerName = c.Customer.Name,
Categories = Categories.Where(cat => cat.Id == c.Customer.Id)
}));
Output
Table Structure
Table Data
If you need all categories couldn't you just:
Categories = (from c in context.Category
select cat)
Good Evening everyone,
I've been trying to figure out the most efficient way to do this, but am falling short. Here's how it goes...
I am ultimately trying to determine "like customers" based on a specific customer's buying habits and a given threshold, say 50%. IE customer 1 purchased products A,B,C,D ... customer 2 purchased B,C,D,E ... these two customers are >= 50% "likeness" so they should be matched.
My schema is as would be expected
CLIENT (1 ----- many) CLIENT_PURCHASE (1 -------many) PRODUCT
*clientID *clientID *prodID *prodID
For now I am ignoring the threshold and simply am trying to find customers who have purchased any item within customer 1's history. I think I have this working with the following two queries:
var clientOneHistory = (from cp in client.Client_Purchase
select cp.prodID).ToList();
var matchedClients = (from cp in db.Client_Purchase
where clientOneHistory.Contains(cp.prodID)
select cp.Client.fullname).Distinct().ToList();
So my ultimate question is, "How do I work in the threshold portion?"
Thanks for your time
I'm not sure exactly how to form these queries for your particular case. Assuming you want to use LINQ-to-SQL. Instead, I'll use the NorthWind database as an example to do the same thing. You could then use the ideas used here in your implementation. I don't think it's possible to do this completely using LINQ-to-SQL, you'll have to do a mix.
var threshold = 0.5M;
// let's pick a customer id
var myId = "VINET";
// get products of current customer
var myProducts = (from c in db.Customers
where c.CustomerID == myId
join o in db.Orders on c.CustomerID equals o.CustomerID
join od in db.Order_Details on o.OrderID equals od.OrderID
select od.ProductID)
.Distinct()
.ToArray();
// get the products of all other customers
var others = (from c in db.Customers
where c.CustomerID != myId
join o in db.Orders on c.CustomerID equals o.CustomerID
join od in db.Order_Details on o.OrderID equals od.OrderID
group od.ProductID by c.CustomerID into g
select new { CustomerID = g.Key, Products = g.Distinct() })
.AsEnumerable();
// calculate "likeness" values for each person
var likeness = from o in others
let Percent = Decimal.Divide(myProducts.Intersect(o.Products).Count(), myProducts.Length)
where Percent >= threshold
select new { o.CustomerID, Percent };