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How to perform LINQ joins with multiple fields in a single join?
Note: this is an aggregate of the answer provided for this question.
I want to get the LINQ equivalent of the following from SQL:
SELECT ..
FROM entity1 e1
JOIN entity2 e2 ON e1.field1 = e2.field1 AND e1.field2 = e2.field2
What is the best way to write the LINQ query?
1 answer
The quickest way is to make an equal join on two anonymous objects:
var result = from x in entity
join y in entity2 on new { x.field1, x.field2 } equals new { y.field1, y.field2 }
Another way is combine the styles of writing the LINQ statements for more flexibility:
var result = from x in entity1
from y in entity2
.Where(y => y.field1 == x.field1 && y.field2 == x.field2)
This allows for more complex JOIN operations and can be easily transformed into a LEFT JOIN by simply adding a .DefaultIfEmpty() at the end.
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