Nullable value types in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a nullable integer variable.

C Sharp (C#)

int[1] number = null;

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

A!

B?

C*

D&

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!' instead of '?' to declare nullable types.

Trying to assign null to a non-nullable value type.

In C#, adding a ? after a value type makes it nullable.

2fill in blank

medium

Complete the code to check if a nullable integer has a value.

C Sharp (C#)

if (number[1]) {
    Console.WriteLine("Has value");
}

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

A.HasValue

B== null

C!= null

D.Value

Attempts:

3 left

💡 Hint

Common Mistakes

Using '== null' to check for value presence instead of 'HasValue'.

Using '.Value' without checking if the value exists.

The HasValue property returns true if the nullable variable contains a value.

3fill in blank

hard

Fix the error in accessing the value of a nullable integer safely.

C Sharp (C#)

int value = number[1];

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A.Value

B== null

C!

D?? 0

Attempts:

3 left

💡 Hint

Common Mistakes

Using '.Value' without checking for null, causing exceptions.

Using '!' which is not valid here.

The null-coalescing operator ?? provides a default value if number is null, avoiding exceptions.

4fill in blank

hard

Fill both blanks to declare a nullable double and assign a value if it is null.

C Sharp (C#)

double[1] temperature = null;
double actualTemp = temperature [2] 25.0;

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

A?

B??

C+

D!

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' instead of '??' for default value.

Forgetting to make the type nullable.

The ? makes the double nullable, and ?? assigns 25.0 if temperature is null.

5fill in blank

hard

Fill all three blanks to create a nullable bool, check if it has value, and get the value or default to false.

C Sharp (C#)

bool[1] isActive = null;
if (isActive[2]) {
    bool status = isActive[3] false;
}

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

A?

B.HasValue

C??

D!

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!' instead of '?' for nullable.

Checking null with '== null' instead of '.HasValue'.

Using '+' instead of '??' for default value.

The ? makes the bool nullable, .HasValue checks if it has a value, and ?? provides a default if null.