linq join 3 tables with or condition

Question

I need to create a statement in LINQ with 3 tables and OR condition.

My function receives an integer, lets call it intZ. I have 3 tables: tableA, tableB and tableC.

tableA has columns int1, int2 and intB. intB is related to tableB.

problem: int1 or int2 of tableA can be intZ and it has to match with one tableC record.

I need an OR condition, but I have no idea where to place it. Does it go in the where clause? Or in the equals clause?

At the moment, I know how to join 3 tables, but the condition is killing me.

What is the difference between the two ways to create statements in linq? Is there a performance impact?

edit: Okay, now I think it's more clear. intZ has to be related with intC from tableC, and this number can be int1 or int2 of tableA.

Answer 1

Just add it to a Where. In Linq2Sql this will be translated to an inner join (with or) on tableB

from a in tableA
from b in tableB.Where(x => x.A == a.A || x.B == a.B)
select new { a, b };

Answer 2

You can't use an "or" condition in joins in LINQ, as it only supports equijoins. But you should be able to do it in a where clause with no problems. For example:

var query = from rowC in tableC
            where rowC.intC == intZ
            from rowA in tableA
            where rowA.int1 == rowC.intC || rowA.int2 == rowC.intC
            join rowB in tableB on rowA.intB equals rowB.intB
            select new { rowA, rowB, rowC };