Question

I have specific SQL expression :

{
select * from courceMCPD.dbo.Contact c 
where c.cID in ( select cId from courceMCPD.dbo.Friend f where f.cId=5)
}

i would like to get LINQ expression that gets the same result.

thank you in advance.

Answer 1

That sounds like it’s equivalent to something like:

var friendIds = from friend in db.Friends
                where friend.ContactId == 5
                select friend.ContactId;

var query = from contact in db.Contacts
            where friendIds.Contains(contact.Id)
            select contact;

(There are lots of different ways of representing the query, but that’s the simplest one I could think of.)

It’s pretty odd to perform a join on a particular field and also mandate that that field has to have a particular value though… there’s not very much difference between that and:

var query = db.Contacts.Where(c => c.Id == 5);

… the only difference is whether there are any friend entries for that particular contact.

EDIT: Smudge gave another option for the query in a comment, so I’m promoting it into this answer…

var query = db.Contacts.Where(c => c.Friends.Any(f => f.cId == 5))

This assumes you’ve got an appropriate Friends relationship defined in the Contacts entity.