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

Practice - 5 Tasks

1fill in blank

easy

Complete the code to safely access the Length property of the string variable.

C Sharp (C#)

int? length = name[1]Length;

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

A?.

B.

C->

D::

Attempts:

3 left

💡 Hint

Common Mistakes

Using the dot operator (.) causes a NullReferenceException if the object is null.

The null-conditional operator ?. safely accesses members only if the object is not null.

2fill in blank

medium

Complete the code to safely call the ToUpper method on the string variable.

C Sharp (C#)

string? upperName = name[1]ToUpper();

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

A.

B->

C?.

D::

Attempts:

3 left

💡 Hint

Common Mistakes

Using the dot operator (.) causes a NullReferenceException if the object is null.

The null-conditional operator ?. calls the method only if the object is not null, avoiding exceptions.

3fill in blank

hard

Fix the error in the code to safely get the length of the string or return 0 if null.

C Sharp (C#)

int length = name[1]Length ?? 0;

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

A?.

B.

C->

D::

Attempts:

3 left

💡 Hint

Common Mistakes

Using the dot operator (.) causes a NullReferenceException if the object is null.

The null-conditional operator ?. returns null if name is null, so the null-coalescing operator ?? can provide a default value.

4fill in blank

hard

Fill both blanks to safely access the first character of the string or return '?' if null or empty.

C Sharp (C#)

char firstChar = name[1]Length > 0 ? name[2][0] : '?';

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

A?.

B.

C??

D->

Attempts:

3 left

💡 Hint

Common Mistakes

Using dot operator (.) to check Length without null check causes exceptions.

Using null-coalescing operator (??) incorrectly in this context.

Use ?. to safely check Length, then use . to index because the condition ensures name is not null or empty.

5fill in blank

hard

Fill all three blanks to safely get the length of the first string in the array or return 0 if null.

C Sharp (C#)

int length = names[1]Length > 0 ? names[0][2]Length [3] 0 : 0;

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

A?.

B??

C:

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Not checking if array is null before accessing Length.

Forgetting to provide default value with null-coalescing operator.

Use ?. to check if names is not null before accessing Length, ?. to safely access the Length of the first element, ?? to provide default 0 if the first string is null. The ternary returns 0 if array is null or empty.