Linq – left join on multiple (OR) conditions

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LINQ only directly supports equijoins. If you want to do any other kind of join, you basically need a cross-join and where:

from a in tablea
from b in tableb
where a.col1 == b.col1 || a.col2 == b.col2
select ...

It’s probably worth checking what the generated SQL looks like and what the query plan is like. There may be more efficient ways of doing it, but this is probably the simplest approach.

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