Question

I am using multiple joins in a statement and Have tried to make linq-to-SQl query for this but no success.

SELECT ur.UserName, ur.LandmarkRef, lt.Date, l.Place
FROM
    tbl_Users ur 
    LEFT OUTER JOIN tbl_LandMarks l ON ur.LandmarkRef = l.LandMarkID
    INNER JOIN tbl_LandmarkTypes lt ON l.LandmarkTypeRef equals lt.LandmarkTypeID

    WHERE ur.UserId == pUserId 

following is the Linq-to-SQL query which does not work if I use LEFT OUTER JOIN

UserDBDataContext lDc = new UserDBDataContext();
var lU= (from ur in lDc.tbl_Users 
         join l in lDc.tbl_LandMarks on ur.LandmarkRef equals l.LandMarkID into Lmark
         from lmk in Lmark.DefaultIfEmpty()
         join lt in lDc.tbl_LandmarkTypes on lmk.LandmarkTypeRef equals lt.LandmarkTypeID 

         where ur.UserId == pUserId                                  
         select new { ur.UserName, ur.LandmarkRef, lc.Date, lmk.Place});

Here Landmark is actually an optional field so it may be NULL so in this case LEFT join does not work and return no row because of NULL value in Landmark. which works in SQL but not in LINQ-to-SQL.

Answer 1

It looks like you may need to make the second join a left outer join as well, using the into syntax.

See this example.