c# - Simple Example Subquery Linq -

t-sql query

select * dbo.user_users userid in (select userid course_enrollments) 

linq entities alternative of above query

var innerquery = en in course_enrollments select en.userid;  var query = u in user_users innerquery.contains(u.userid) select u; 

there alot of complex subqueries on stackoverflow, want see simple example of how simple subquery done via linq.this how done it, not because sends 2 queries database.

simple answer use "let" keyword , generate sub-query supports conditional set main entity.

var usersenrolledincourses = u in user_users                                  let ces = ce in course_enrollments                                            select ce.userid                                  ces.contains(u.userid)                              select u;    

this create exists block in tsql similar to

select [extent1].*    dbo.user_users extent1    exists (select 1 [c1]                      dbo.course_enrollements extent2                      (extent2.userid = extent1.userid)) 

it's close you've asked , create same query plan on sql server.

hope helps!