Question

In SQL, it’d be done as such:

SELECT * FROM Student
WHERE SchoolId IN
    (SELECT id FROM School WHERE Name LIKE '%elementary%')

How do I implement this with LINQ? I’ve tried the following:

var list = context.Students.Where(x => context.Schools.Where(r => r.Name.Contains("elementary").Select(r => r.Id).Contains(x.SchoolId))

but it’s not giving me what I want, unfortunately…

I know it’s possible to retrieve all the Ids from the School table first, but I think it’d take a heavy toll on the performance. Preferably I’d like LINQ to SQL to handle everything; I can’t do this using vanilla SQL because I need stuff to be dynamic and currently LINQ is the best solution for me.

The code above is all for illustration purposes; what I’m doing is a tad different (but more or less the same). I really do need some help on this; if you need any more information just feel free to ask.

EDIT: My bad, I missed out a field. It works, but the results didn’t show up because I was missing that field… So sorry…

Answer 1

Something like this should work. The first use of Contains is on a string object to see if the string contains the substring “elementary”. The second use of Contains is on a list and checks to see if the first result list contains SchoolId.

var sublist = from s in context.Schools
              where s.Name.Contains("elementary")
              select id;

var list = from s in context.Students
           where sublist.Contains(s.SchoolId)
           select s;