LINQ Query Using OR Condition in JOIN Clause

Question

2.33/5 (2 votes)

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Note: C# or VB.NET answers are fine, but my question will be in VB.NET...

I have been trying to convert the following SQL into a LINQ to Entity statement:

SQL

SELECT
	*
FROM Person
JOIN Company
	ON Person.CompanyName = Company.CompanyName
	OR
	(
		Person.CompanyName = 'Unemployed'
		AND Company.VolunteerJob = 1
	)

However, LINQ does not seem to support the OR operator in JOIN clauses. A coworker of mine helpfully suggested I use a UNION, which I will try tomorrow, but I'd like to know if there is a more obvious syntax. To clarify, this is what I am trying to do (the syntax does not support this):

VB.NET

Dim results =
    From Person In context.Person
    Join Company In context.Company
        On Person.CompanyName Equals Company.CompanyName Or
        (Person.CompanyName Equals "Unemployed" And Company.VolunteerJob = 1)

Note that the tables/fields I am really using are nothing like the above... I am just using them above for demonstration purposes.

Posted 11-Jul-11 14:02pm

AspDotNetDev

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2 solutions

Solution 1

Hi,

try using LINQ pad from here[^]

OR is written as || in LINQ

also check this[^]

Posted 11-Jul-11 21:37pm

Syed Salman Raza Zaidi

Updated 11-Jul-11 21:43pm

v2

Comments

AspDotNetDev 12-Jul-11 11:11am

FYI, I voted you a 2 because this is not an answer. || in C# is the same as OR in VB.NET, which doesn't help me much because that operator apparently can't be used in a JOIN. I already have LINQPad, yet I don't magically have an answer from it. Was there something specific at the link you sent me to that has an answer, or is it just another general LINQ resource?

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AspDotNetDev · Accepted Answer · 2011-07-12T08:16:00

There are two approaches I am considering, but I have to look into the performance before I decide. One approach puts all the conditions in the WHERE clause, and the other approach UNIONs two initial result sets.

VB.NET

' Get all companies in one LINQ query.
Dim combinedCompanies =
	From P in context.Person
	From C in context.Company
	Where
		C.CompanyName Equals P.CompanyName
		And P.CompanyName <> "Unemployed"
		Or
		(
			P.CompanyName = "Unemployed" And
			C.VolunteerJob = True
		)

This is the version that my coworker recommended:

VB.NET

' Join with normal companies.
Dim matchingCompanies =
	From P In context.Person
	Join C In context.Company
		On C.CompanyName Equals P.CompanyName
	Where
		P.CompanyName <> "Unemployed"

' Join with volunteer companies.
Dim volunteerCompanies =
	From P In context.Person
	From C In context.Company
	Where
		P.CompanyName = "Unemployed" And
		C.VolunteerJob = True

' Combine normal and volunteer companies.
Dim combinedCompanies = matchingCompanies.Union(volunteerCompanies)

I like the brevity of the first approach, but I'm not sure it will be as performant as the second approach.