Question

I wonder if anyone can help

I have a simple SQL Query which was this.

SELECT * FROM ITEM INNER JOIN CODES ON ITEM.ITEMID = CODES.ITEMID AND
        ITEM.CATID = CODES.CATID

This works great, so i created the following query in LINQ

from i in Item join  c in codes
      on new { i.itemid, i.catid } equals new { c.itemid, c.catid }

Works great, but they i realized that i actually needed an LEFT JOIN in place of the INNER JOIN. So the sql, which now works great!, is :- (notice left join)

SELECT * FROM ITEM LEFT JOIN CODES ON ITEM.ITEMID = CODES.ITEMID AND
        ITEM.CATID = CODES.CATID

So now everything seems to work and i get back the data i require using SQL i can’t figure out how to do a left join in LINQ and especially how to do a left join on more than 1 field – in my case itemid and catid

I wonder if anyone can lend a hand, i am stuck 🙂

Answer 1

I think this is the direction you need to head down:

from i in Item 
   join c in codes on new { i.itemid, i.catid } equals new { c.itemid, c.catid } 
   into grouped
   from g in grouped.DefaultIfEmpty()
   select new
   {
      ItemId = c.itemid,
      CatItemId = g != null ? g.itemid : "Empty"
   };