LINQ performance considerations in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to use LINQ to filter numbers greater than 10.

C Sharp (C#)

var result = numbers.Where(n => n [1] 10);

Drag options to blanks, or click blank then click option'

A==

B<

C>

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' will select numbers less than 10, which is incorrect.

Using '==' selects only numbers equal to 10, not greater.

The 'Where' method filters elements. Using '>' selects numbers greater than 10.

2fill in blank

medium

Complete the code to convert the filtered result to a list for better performance.

C Sharp (C#)

var list = result.[1]();

Drag options to blanks, or click blank then click option'

AWhere

BToArray

CSelect

DToList

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Where' again does not materialize the query.

Using 'Select' is for projection, not materialization.

Using 'ToList()' materializes the query immediately, improving performance when enumerating multiple times.

3fill in blank

hard

Fix the error in the LINQ query to avoid multiple enumerations causing performance issues.

C Sharp (C#)

var count = [1].Count();
var first = numbers.First();

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Anumbers

Bnumbers.Select(n => n * 2)

Cnumbers.Where(n => n > 5)

Dnumbers.OrderBy(n => n)

Attempts:

3 left

💡 Hint

Common Mistakes

Using a query expression directly causes it to run multiple times.

Not materializing the query can cause performance hits.

Using 'numbers' directly avoids multiple enumerations of a query, which can be costly.

4fill in blank

hard

Fill both blanks to create a dictionary from a list with keys as IDs and values as names.

C Sharp (C#)

var dict = people.ToDictionary(p => p[1], p => p[2]);

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A.Id

B.Name

C.Age

D.Address

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-unique fields as keys causes runtime errors.

Swapping key and value selectors leads to incorrect dictionary.

'ToDictionary' needs a key selector and a value selector. Here, keys are IDs and values are Names.

5fill in blank

hard

Fill all three blanks to create a filtered and projected list of uppercase names for people older than 30.

C Sharp (C#)

var result = people.Where(p => p[1] > 30).Select(p => p[2].[3]()).ToList();

Drag options to blanks, or click blank then click option'

A.Age

B.Name

CToUpper

DToLower

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'ToLower' instead of 'ToUpper' changes the case incorrectly.

Filtering by wrong property leads to wrong results.

Filter by age > 30, select the Name property, then convert it to uppercase.