LEFT JOIN with OR Condition

Question

How can I represent the following LEFT JOIN in Entity Framework?

SELECT * FROM a 
LEFT JOIN b ON 
(a.UserId = b.Field1 AND b.Field2 = SOME_VARIABLE) 
OR (a.UserId = b.Field2 AND b.Field1 = SOME_VARIABLE)

For ANDs I know I can use complex anonymous types and EQUALS but I can't figure out how to handle ORs?

Answer 1

var query = from a in context.aTable
            select new {
               A = a,
               B = (from b in context.bTable
                     where (a.UserId == b.Field1 && b.Field2 == SOME_VARIABLE) ||
                           (a.UserId == b.Field2 && b.Field1 == SOME_VARIABLE)
                    select b
                   ).DefaultIfEmpty()
            }

You can ignore DefaultIfEmpty depending on your need.