Problems with Linq-to-SQL join query - sql

Question

var grid = new System.Web.UI.WebControls.GridView();
grid.DataSource = from booking in bookings
join f in getallAttendees on booking.UserID equals f.UserID into fg
from fgi in fg.DefaultIfEmpty() //Where(f => f.EventID == booking.EventID)
where
booking.EventID == id
select new
{
EventID = booking.EventID,
UserID = booking.UserID,
TrackName = booking.Name,
BookingStatus = booking.StatusID,
AttendeeName = booking.FirstName,
// name = account.FirstName,
AmountPaid = booking.Cost,
AttendeeAddress = booking.DeliveryAdd1,
City = booking.DeliveryCity,
Postcode = booking.Postcode,
Date = booking.DateAdded,
product = fgi == null ? null : fgi.productPurchased
};
Booking table design:
ID, EventID, UserID, BookingStatus, AmountPaid, AttendeeAddress, City, Date
Product table design:
ID, EventID, SecondDriver, Apples, Bananas, SecondItem
The association between booking and product table is many to many and the foreign key is UserID
The above Linq-to-SQL query returns the data of only users whose booking.UserID equals att.UserID, what I want is to return all the users of that particular event also with apples and banana fields if they have bought else fill null in that columns.
Any possible solutions or examples will be highly appreciated.

Answer 1

I think you are looking for an equivalent to a Left Join. You can accomplish this by using the DefaultIfEmpty() extension method. Modify your join statement and add another from in like so:
join at in getallAttendees on booking.UserID equals at.UserID into attg
from att in attg
In your select statement you can use the ternary operator ? : like so:
SecondItem = att == null ? null : att.SecondItem,
Edit
Your bookings and getallAttendees IQueryable need to come from the same context if you want to join them together.
Otherwise you will need to use getallAttendees.ToList() and bookings.ToList()