You are developing a new feature in the application to display a list of all bundled products.
You need to write a LINQ query that will return a list of all bundled products. Which query expression should you use?
A.
context.Parts.Cast<Product>()
.Where(p => p.Descendants.Any(d => d is Product))
B.
context.Parts.OfType<Product>()
.Where(p => p.Descendants.Any(d => d is Product))
C.
context.Parts.Cast<Product>()
.ToList()
.Where(p => p.Descendants.Any(d => d is Product))
D.
context.Parts.OfType<Product>()
.ToList()
.Where(p => p.Descendants.Any(d => d is Product))
Explanation:
OfType() Filters the elements of an IEnumerable based on a specified type.Enumerable.OfType<TResult> Method
(http://msdn.microsoft.com/en-us/library/bb360913.aspx)
1) Very unclear question. may be class diagram is lost? 2) why not B?
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I agree, unclear and a diagram would have been helpful to say the least.
The only reason I can think of to prefer D in favor of B is “…that will return a list…”, a list instead of some generic collection.
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This is just a guess, but I think ToList() is required in order to use the “is” operator, since I don’t think LINQ maps that operator to SQL like it does with OfType().
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I agree wuth Gaius, linq to sql queryprovider probably won’t parse “is” statement
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It’s D because B returns IQuerable. The Enumerable.OfType() method is implemented by using deferred execution.
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Thanks for the answer! 🙂
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