Linq - Correct format for Left Join

Question

I am new to linq... and I am wondering if I am doing it right..

Here's my code...

var result = from a in ctx.ItemReceipts
             join b in ctx.ItemReceiptStatusTypes on a.Status equals b.ItemReceiptStatusTypeID
             join c in ctx.PurchaseOrders on a.ReferenceID equals c.PurchaseOrderID
             into leftJoinItemReceipts 
             from d in leftJoinItemReceipts.DefaultIfEmpty()
             where a.ItemReceiptID.Equals(ItemReceiptID)
             select new
             {
                 CItemReceiptID = a.ItemReceiptID,
                 CTransactionNumber = a.TransactionNumber,
                 CRemarks = a.Remarks,
                 CStatus = a.Status,
                 CStatusType = b.Description,
                 CReferenceID = a.ReferenceID,
                 CReferenceTypeID = a.ReferenceTypeID,
                 CTransactionDate = a.TransactionDate,
                 CDateReceived = a.DateReceived,
                 CTotalCost = a.TotalCost,
                 CPONumber = d.PONumber                     
             };

It runs perfectly... but I really can't understand the into part.. I dunno if it's really a left join but gives me the data that I want... it gives me all data in itemreceipts even though they don't have something in common with PurchaseOrder....

I need explanation... better a comparison between mysql and linq...

mysql and linq are two completely different things, is this c# or vb? — Sayse, Nov 26 '15 at 07:29
@Sayse this is C#... yes they are.... and I am new to linq... so bear with me. — Sam Teng Wong, Nov 26 '15 at 07:30
You may want to look at this webpage.: https://code.msdn.microsoft.com/101-LINQ-Samples-3fb9811b — jdweng, Nov 26 '15 at 07:36
based on this article http://www.basepointers.com/performing-inner-join-cross-join-left-and-right-outer-joins-using-linq-queries.. it is most likely to be `outerjoin`... it will get all records from both table even though they don't have something in common. — Sam Teng Wong, Nov 26 '15 at 07:42

score 0 · Answer 1 · answered Nov 26 '15 at 07:36

0

from a in ctx.ItemReceipts
join b in ctx.ItemReceiptStatusTypes on a.Status equals b.ItemReceiptStatusTypeID
into leftJoinItemReceipts 
from d in leftJoinItemReceipts.DefaultIfEmpty()
join c in ctx.PurchaseOrders on d.ReferenceID equals c.PurchaseOrderID

This will do a left join on ItemReceipts and ItemReceiptStatusTypes and then a inner join with PurchaseOrders

answered Nov 26 '15 at 07:36

Nambirajan S

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1
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what's the difference? – Sam Teng Wong Nov 26 '15 at 07:41
ItemReceipts will do a inner join with ItemReceiptStatusTypes and the ItemReceiptStatusTypes will be left joined with PurchaseOrders on your query – Nambirajan S Nov 26 '15 at 07:44
it is the same query with mine I guess. the position just interchange. – Sam Teng Wong Nov 26 '15 at 07:47
ItemReceipts should left join with ItemReceiptStatusTypes or PurchaseOrders ? – Nambirajan S Nov 26 '15 at 07:53
what I want is ItemReceipt will do inner join in StatusType and ItemReceipt should be left join with PurchaseOrder... – Sam Teng Wong Nov 26 '15 at 07:55
then urs is correct, if it needs to left join with ItemReceiptStatusTypes follow mine – Nambirajan S Nov 26 '15 at 07:57
Sure sir.... thanks =) – Sam Teng Wong Nov 26 '15 at 08:01

Linq - Correct format for Left Join

1 Answers1