You are developing an application in Visual Studio 2012 to display student information. The application
contains the following Entity Framework model.
The application contains a WCF data service named DirectoryService.svc.
You need to create a query expression to display all of the grades for students whose first name is
“John”
How should you build the expression?
A.
http://localhost:54946/DirectoryService.svc/Students?$filter=FirstName eq ‘John’ &$expand=Grades
B.
http://localhost:54946/DirectoryService.svc/Students?$filter=FirstName eq ‘John’/Grades
C.
http://localhost:54946/DirectoryService.svc/Students?$filter=FirstName = ‘John’ &$expand=Grades
D.
http://localhost:54946/DirectoryService.svc/Grades/Students?$filter=FirstName eq ‘John’
C
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No, A
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Why A?
I think D.
Quote from ‘Ryan W. Exam Ref 70-487’:
“As long as there are relationships defined in the Entity Model, you can use a few different semantics to return related entities.
…
Change things up and assume (just for review) that you want to return the Question entity with a key value of “1” and you want just the QuestionText property:
http://servicehost/ExamPrepService.svc/Questions('1‘)/QuestionText
That would give you the Question text, but what if you wanted the Answers to it? You would use:
http://servicehost/ExamPrepService.svc/Questions('1‘)/Answers
You can work it the other way around, too, of course. If you want the Question that corresponded to an Answer entity with a key of (‘1:4’):
http://servicehost/ExamPrepService.svc/Answers('1:4‘)/Question”
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D will return Students, while we need Grades.
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So I think that A is correct.
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Answer is
A. http://localhost:54946/DirectoryService.svc/Students?$filter=FirstName eq ‘John’ &$expand=Grades
https://www.odata.org/documentation/odata-version-2-0/uri-conventions/
The syntax of a $expand query option is a comma-separated list of Navigation Properties. Additionally each Navigation Property can be followed by a forward slash and another Navigation Property to enable identifying a multi-level relationship.
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