Exam 70-487 All Questions

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Exam 70-487 topic 1 question 17 discussion

Actual exam question from Microsoft's 70-487

Question #: 17
Topic #: 1

You are developing an ASP.NET MVC application. The application is an order processing system that uses the ADO.NET Entity Framework against a SQL Server database. It has a controller that loads a page that displays all orders along with customer information. Lazy loading has been disabled.
The Order class is shown below.

You need to return the orders and customer information in a single round trip to the database.
Which code segment should you use?

A. Option A
B. Option B
C. Option C
D. Option D

Show Suggested Answer

Suggested Answer: A 🗳️

by supersunny at Feb. 17, 2020, 10:53 a.m.

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supersunny

Highly Voted 5 years, 4 months ago

This is the case of lazy loading so A is suitable.

upvoted 10 times

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Dreamchaser1980

Highly Voted 4 years, 9 months ago

The answer is A. Using the include statement is called eager loading. The IQueryable<Order> query is executed on the database when it is returned to the View in the orders.ToList() statement, this is called deferred execution. So there is only one roundtrip to the database. I double checked the code on my computer.

upvoted 8 times

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Ptu12125

Most Recent 4 years, 5 months ago

Lazy loading is disabled. Correct answer is C. "Loading of related entities can still be achieved using eager loading (see Eagerly Loading above) or the Load method (see Explicitly Loading below)." Ref: https://docs.microsoft.com/en-us/ef/ef6/querying/related-data

upvoted 1 times

Ptu12125

4 years, 5 months ago

Sorry, A is correct due to deferred execution, it will call the query only once.

upvoted 1 times

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Tinashe16

4 years, 6 months ago

A is correct. For eager loading, use Include keyword, and it should be immediately after your DbSet.

upvoted 2 times

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mmk1991

5 years, 3 months ago

Correct answer is C, since it says lazy loading has been disabled. See ExplicitLoading in https://docs.microsoft.com/en-us/ef/ef6/querying/related-data

upvoted 5 times

Karel_Gott

5 years, 3 months ago

Lazy loading has been DISABLED means, that entities will be loaded automatically when you ACCESS them. So the correct answer is A.

upvoted 3 times

nsch

5 years, 3 months ago

Even with lazy loading disabled it is still possible to lazily load related entities, but it must be done with an explicit call. To do so you use the Load method on the related entity’s entry. https://docs.microsoft.com/en-us/ef/ef6/querying/related-data

upvoted 1 times

SirMarv

5 years, 2 months ago

Very correct that we can still lazily load related entities, but that analogy would apply if we were trying to lazily load entities even with Lazy Loading disabled, so A is the correct answer.

upvoted 3 times

tanujgyan

5 years ago

In my opinion A is correct. Its Eager loading. Also whenever they talk about explicit loading they mention Reference or Collection methods and not select method and I might be wrong here but I dont think C will work

upvoted 5 times

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mchen

5 years, 2 months ago

C is correct

upvoted 2 times

mr_

4 years, 11 months ago

In my opinion C is wrong. Correct answer is A. '(...) in a single round trip to the database' C is wrong because it will perform two round trips to the DB - first on Load(), second on ToList(). Answer A is correct because there will be single round trip (single SELECT-LEFT-JOIN statemet). Tested with SQL Server Profiler.

upvoted 8 times

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mmk1991

5 years, 3 months ago

Relevant docs: https://docs.microsoft.com/en-us/ef/ef6/querying/related-data

upvoted 1 times

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