GroupBy operation in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to group numbers by their remainder when divided by 3.

C Sharp (C#)

var groups = numbers.[1](n => n % 3);

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

ASelect

BWhere

CGroupBy

DOrderBy

Attempts:

3 left

💡 Hint

Common Mistakes

Using Select instead of GroupBy will transform elements but not group them.

Where filters elements but does not group.

OrderBy sorts elements but does not group.

The GroupBy method groups elements based on a key selector function.

2fill in blank

medium

Complete the code to print each group key and its elements.

C Sharp (C#)

foreach (var group in groups) {
    Console.WriteLine($"Key: {group.[1]");
    foreach (var num in group) {
        Console.WriteLine(num);
    }
}

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

ACount

BKey

CToList

DElementAt

Attempts:

3 left

💡 Hint

Common Mistakes

Using Count instead of Key will print the number of elements, not the key.

ToList is a method, not a property, and does not represent the key.

ElementAt requires an index and is not the key.

The Key property gives the key value of each group.

3fill in blank

hard

Fix the error in the code to group words by their first letter.

C Sharp (C#)

var groupedWords = words.[1](w => w[0]);

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

AGroupBy

BWhere

CSelect

DOrderBy

Attempts:

3 left

💡 Hint

Common Mistakes

Using Select or Where instead of GroupBy will not create groups.

OrderBy sorts but does not group.

GroupBy is needed to group elements by a key, here the first letter.

4fill in blank

hard

Fill both blanks to create a dictionary from groups with key and count of elements.

C Sharp (C#)

var dict = groupedWords.ToDictionary(g => g.[1], g => g.[2]());

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AKey

BCount

CLength

DSum

Attempts:

3 left

💡 Hint

Common Mistakes

Using Length is invalid for groups; Count() is the correct method.

Sum is for adding values, not counting elements.

Use Key for the dictionary key and Count() to get the number of elements in each group.

5fill in blank

hard

Fill all three blanks to group numbers by even/odd and select the key and sum of each group.

C Sharp (C#)

var result = numbers.[1](n => n % 2 == 0).Select(g => new {
    [2] = g.Key,
    [3] = g.Sum()
});

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

AGroupBy

BKey

CSum

DCount

Attempts:

3 left

💡 Hint

Common Mistakes

Using Count instead of Sum will count elements, not sum them.

Using Select instead of GroupBy will not group elements.

GroupBy groups numbers by even/odd, Key accesses the group key, and Sum calculates the total of each group.