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 customers. Customers are filtered on Country and,
if provided, on CompanyName.
You have an Entity Framework context named db.
The Customer class is shown below.
You need to execute a single deferred query to return the filtered list of customers. Which
code segment should you use?
A.
Option A
B.
Option B
C.
Option C
D.
Option D
I don’t think that C is the correct answer because of the call to .Load(), this causes the query to execute immediately which is not what the question is asking for.
My preferred answer would be A
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The Load extension method works just like ToList, except that it avoids the creation of the list altogether. So after calling Load, the data is filtered without any other trip to DB..
I think C is correct.
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Why even call Load? I think correct answer is A.
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If you used A, in the case where you don’t provide a value for CompanyName, the method will return null. customers isn’t assigned a value unless CompanyName has a value.
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A is correct answer. (If ComapanyName is provided)
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Customers collection will always be null if the CompanyName is not provided. I think this question is wrong…
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Yes, you are right.
From this cases i prefer “A” as closest one, not “C”
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Answer should be A.
In case of C, won’t it cause 2 round trip to server since DBContext is queried twice ?
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Beside A and B is the same…
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No it is not the same, A: IEnumerable twice and in B: once.
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In the exam, i will go for A !
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A, C and D run ! But a single deferred query we have only at A.
“IEnumerable has immediate execution, whereas IQueryable has deferred execution or lazy loading”
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