How to achieve Left Excluding JOIN using LINQ?

Question

How to achieve Left Excluding JOIN using LINQ?

In SQL:

SELECT <select_list>  FROM Table_A A LEFT JOIN Table_B B ON A.Key = B.Key WHERE B.Key IS NULL 

Answer 1

You need DefaultIfEmpty() for the LEFT JOIN, then you can check if the joined value is null:

var result = from a in Table_A              join b in Table_B on a.Key equals b.Key into j              from b in j.DefaultIfEmpty()              where b == null              select new { ... }; 

Answer 2

Easier would be to write like this:

var result = from a in Table_A              where !Table_B.Any(b => b.Key == a.key)              select new { ... };