Linq to sql double inner join statement

Question

I am trying to write a linq to sql statement that will join a total of 3 tables. table 1 = users (userId) tabe 2 = userCourses (userId, CourseId), table 3 = courses(courseId).

This is what i am trying to do:

from u in db.Users join uc in userCourse on u.userId = uc.Id
                   join c in course on uc.courseId = c.courseId

                   where u.userId = uc.userId
                   select c.name

what is the proper syntax?

Duplicate: http://stackoverflow.com/questions/37324/what-is-the-syntax-for-an-inner-join-in-linq-to-sql — Jacco, Feb 07 '13 at 21:31
see also http://stackoverflow.com/q/7229569/146077 - why are you using `join` at all? — Kirk Broadhurst, Feb 12 '13 at 02:04

score 4 · Accepted Answer · answered Feb 07 '13 at 21:29

You are almost there, assuming your key types match. You just need to use the equals keyword in the join clauses:

from u in db.Users join uc in userCourse on u.userId equals uc.Id
                   join c in course on uc.courseId equals c.courseId   
                   where u.userId = uc.userId
                   select c.name

This is one of the few places where LINQ is slightly odd, since we cant use the equality operator in the join clause, but need to use a keyword not used anywhere else in the language. It also means that we can't join on an arbitrary expression.

score 1 · Answer 2 · edited Jul 14 '14 at 13:58

1

Try

from u in db.Users 
join uc in userCourse on u.userId equals  uc.Id
join c in course on uc.courseId equals c.courseId

where u.userId = uc.userId
select c.name

Also refer below link

https://web.archive.org/web/20101030154925/http://blogs.msdn.com/b/tikiwan/archive/2010/06/18/linq-to-sql-inner-join-left-join-examples-tutorial-samples-the-basic.aspx

edited Jul 14 '14 at 13:58

Taryn

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answered Feb 07 '13 at 21:32

DevelopmentIsMyPassion

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Linq to sql double inner join statement

2 Answers2