The outer and inner join LINQ question.

vbboyd · March 16th, 2012, 12:18 AM

Reading through Chapter 14 of your book, I was wondering how does LINQ simulate or emulate inner and outer joins? How does interact and interface with stored procedures?

Thanks once again!

Imar · March 16th, 2012, 05:21 AM

Hi there,

Google is your friend:

101 LINQ Examples including JOIN Syntax: http://code.msdn.microsoft.com/101-L...mples-3fb9811b

LINQ itself doesn't do stored procedures as it's only a query language. However, Entity Framework and LINQ to SQL do support it:

EF: www.google.com/?q=EF+stored+procedures
L2S: www.google.com/?q=LINQ+to+SQL+stored+procedures

Cheers,

Imar

WebDev123 · September 13th, 2012, 11:34 PM

Hello,

Following on vbboyd's question about no join examples in Chapter 14 ...

I have used LINQ-To-SQL once before, but was under the impression that, although the syntax is similar for LINQ in the Entity Framework, it still is different. Is the syntax, in fact, the same? (the weblink Imar gave doesn't explicitly mention Entity Framwork). In other words, are LINQ statements the same across any type of LINQ-To-X

Here is my conceptual understanding. Someone please advise if this is correct: By adding the .Include() method after the entity, you are in effect doing an Inner Join, as now you have access to the related rows in the "included" entity. I am fuzzy on how you would perform the outter join unless it's the same as LINQ-To-SQL.

Thanks everyone.

Imar · September 16th, 2012, 09:59 AM

Quote:

Is the syntax, in fact, the same?

Yes, LINQ as a query language is a stand alone concept that can be used by, for example, L2S and LINQ to Entities. The query language itself is the same in both implementations although the methods they support can be different. Also, managing objects (creating new ones for example) is different because that's not a LINQ feature but an ORM feature.

For an example of an OUTER JOIN with LINQ

http://www.hookedonlinq.com/OuterJoinSample.ashx

And yes, by calling Include you get an INNER JOIN although you don't have to use Include to use an INNER JOIN.

Cheers,

Imar

WebDev123 · September 16th, 2012, 07:01 PM

This is a good post; it's important to understand the concepts behind the tools and implementations. Now I understand why LINQ-To-SQL seemed different than LINQ-To-Entities.

Different methods are exposed, and different constructs are used to manage data objects, depending on which you are using, but the language is the same.

This sheds some clarity on the subject. Thank you.