Null-coalescing operator in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign a default value if 'name' is null.

C Sharp (C#)

string displayName = name [1] "Guest";

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

A||

B??

C&&

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '||' which is a logical OR and does not work with null values.

Using '&&' which is a logical AND and incorrect here.

Using '==' which is a comparison operator, not for assignment.

The null-coalescing operator '??' returns the left-hand operand if it is not null; otherwise, it returns the right-hand operand.

2fill in blank

medium

Complete the code to assign 'result' to 'input' or 0 if 'input' is null.

C Sharp (C#)

int result = input [1] 0;

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

A?:

B&&

C||

D??

Attempts:

3 left

💡 Hint

Common Mistakes

Using '||' which is a logical OR and not for null checks.

Using '?:' which is the ternary operator but more verbose here.

Using '&&' which is logical AND and incorrect.

The '??' operator returns the left operand if it is not null; otherwise, it returns the right operand.

3fill in blank

hard

Fix the error in the code by completing the null-coalescing expression.

C Sharp (C#)

string message = GetMessage() [1] "No message";

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

A||

B&&

C??

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '||' which is a logical OR and not for null fallback.

Using '==' which is a comparison, not assignment.

Using '&&' which is logical AND and incorrect.

The '??' operator correctly provides a fallback value if GetMessage() returns null.

4fill in blank

hard

Fill both blanks to create a dictionary with word lengths only if length is greater than 3.

C Sharp (C#)

var lengths = new Dictionary<string, int> { {"apple", "apple".Length}, {"cat", "cat".Length} };
var filtered = lengths.Where(kv => kv.Value [1] 3).ToDictionary(kv => kv.Key, kv => kv.Value [2] 1);

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

A>

B+

C<

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' for filtering.

Using '-' instead of '+' for incrementing values.

We filter lengths greater than 3 and add 1 to each value in the new dictionary.

5fill in blank

hard

Fill all three blanks to create a dictionary with uppercase keys and values only if value is not null.

C Sharp (C#)

var data = new Dictionary<string, string?> { {"a", "apple"}, {"b", null} };
var result = data.Where(kv => kv.Value [1] null).ToDictionary(kv => kv.Key.[2](), kv => kv.Value.[3]());

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

A!=

BToUpper

CToLower

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '!=' to filter nulls.

Using 'ToLower()' instead of 'ToUpper()' for uppercase conversion.

We filter out null values using '!=', then convert keys and values to uppercase using 'ToUpper()'.