LINQ Equivalent of and SQL query with two inner joins and a left join - linq

Question

I would be grateful for help with a LINQ equivalent of the following SQL Query (which works). Below this SQL query I give some description of my simple data base and the problem I want to solve.
Select a.Name, a.OrderID,
b.ProductIDFirst, c1.productName ProductNameFirst,
b.ProductIDSecond , c2.productName ProductNameSecond
from Customers a
INNER JOIN ORDERS b ON a.OrderID = b.OrderID
left join products c1 on b.productidfirst = c1.productid
left join products c2 on b.ProductIDSecond = c2.productid
Background information on the database structure:
I have a simple SQL Server Database with three Tables named Products, Orders and Customers.
The business model is such that each order can have only two products (not more).
The Orders table has two foreign keys, though they both come from the Products table. These Foreign Key field Names in the Orders Table are ProductIDFirst and ProductIDSecond. These two Foreign Keys in the orders table correspond to two products that each order can have. Customers table has one Foreign Key which comes from the Orders Table.
Now I need help with an LINQ query that will return me all customers such that I get five fields - CustomerName, OrderID and Names of each of the two products that match the OrderID in the customer product.

Answer 1

Your links are non-existent, so here's a best attempt without seeing anything.
Assuming you have the following containers (you'll need to change them for your scenario):
var customers = new List<Customer>();
var orders = new List<Order>();
var products = new List<Product>();
You can do the following:
var query =
from a in customers
join b in orders
on a.OrderId equals b.OrderId
join c1 in products
on b.ProductIdFirst equals c1.ProductId into c1a
join c2 in products
on b.ProductIdSecond equals c2.ProductId into c2a
from p1 in c1a.DefaultIfEmpty()
from p2 in c2a.DefaultIfEmpty()
select new
{
Name = a.Name,
OrderId = a.OrderId,
ProductIdFirst = p1 == null ? null : p1.ProductIdFirst,
ProductNameFirst = p1 == null ? null : p1.ProductNameFirst,
ProductIdSecond = p2 == null ? null : p1.ProductIdSecond,
ProductNameSecond = p2 == null ? null : p1.ProductNameSecond,
};
In short, where you want a left join, project the join into something else (e.g. c1a, c2a) then call from on them using DefaultIfEmpty() which will set null when no matching item exists on the right-hand-side.