Boolean type behavior in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a Boolean variable with the value true.

C Sharp (C#)

bool isActive = [1];

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

Atrue

BTrue

C1

D"true"

Attempts:

3 left

💡 Hint

Common Mistakes

Using capitalized True instead of lowercase true.

Using numeric values like 1 instead of Boolean literals.

Using string "true" instead of Boolean literal.

In C#, the Boolean literal for true is true in lowercase.

2fill in blank

medium

Complete the code to check if the Boolean variable is false.

C Sharp (C#)

if (isEnabled == [1]) {
    Console.WriteLine("Disabled");
}

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

A0

Bfalse

CFalse

DTrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using capitalized False instead of lowercase false.

Using numeric 0 instead of Boolean literal.

Using True instead of false.

The Boolean literal for false in C# is false in lowercase.

3fill in blank

hard

Fix the error in the code to correctly assign a Boolean value.

C Sharp (C#)

bool isReady = [1];

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

A"true"

BTrue

Ctrue

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using string "true" instead of Boolean literal.

Using capitalized True which is invalid in C#.

Using numeric 1 instead of Boolean literal.

Boolean values must be assigned using lowercase true or false without quotes.

4fill in blank

hard

Fill both blanks to create a Boolean expression that checks if x is greater than 10.

C Sharp (C#)

bool result = (x [1] 10) [2] true;

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

A>

B==

C<

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > for greater than.

Using != instead of == for equality check.

Omitting the comparison to true.

The expression x > 10 == true checks if x is greater than 10.

5fill in blank

hard

Fill all three blanks to create a Boolean expression that checks if y is less than or equal to 5 and isActive is true.

C Sharp (C#)

bool check = (y [1] 5) [2] (isActive [3] true);

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

A<=

B&&

C==

D||

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of <= for less than or equal.

Using || instead of && for logical AND.

Omitting == when comparing Boolean values.

The expression (y <= 5) && (isActive == true) checks both conditions correctly.

Practice

1. Which of the following is a valid Boolean value in C#?

easy

A. yes

B. 1

C. 0

D. true

Solution

1. Step 1: Understand Boolean values in C#

   Booleans in C# can only be true or false.

2. Step 2: Check each option

   Only true is a valid Boolean. Numbers or words like yes are not Booleans.

3. Final Answer:

   true -> Option D

4. Quick Check:

   Boolean values = true or false [OK]

Hint: Booleans are only true or false, nothing else [OK]

Common Mistakes:

• Thinking 1 or 0 are Boolean values
• Using strings like 'yes' or 'no' as Booleans
• Confusing integers with Booleans

2. Which of the following is the correct way to declare a Boolean variable in C#?

easy

A. bool isActive = true;

B. boolean isActive = true;

C. Bool isActive = true;

D. bool isActive = "true";

Solution

1. Step 1: Recall C# Boolean declaration syntax

   In C#, the keyword for Boolean type is bool (all lowercase).

2. Step 2: Check each option

   bool isActive = true; uses bool and assigns true correctly. boolean isActive = true; uses boolean which is incorrect in C#. Bool isActive = true; uses Bool with uppercase B, which is invalid. bool isActive = "true"; assigns a string "true" instead of Boolean true.

3. Final Answer:

   bool isActive = true; -> Option A

4. Quick Check:

   Boolean declaration uses 'bool' keyword [OK]

Hint: Use lowercase 'bool' and assign true or false without quotes [OK]

Common Mistakes:

• Using 'boolean' instead of 'bool'
• Capitalizing 'Bool'
• Assigning Boolean as a string

3. What will be the output of the following C# code?

bool a = true;
bool b = false;
Console.WriteLine(a && b);

medium

A. true

B. 1

C. False

D. 0

Solution

1. Step 1: Understand the '&&' operator with Booleans

   The '&&' operator means AND. It returns true only if both sides are true.

2. Step 2: Evaluate the expression

   Here, a is true and b is false. true AND false is false, which Console.WriteLine outputs as False.

3. Final Answer:

   False -> Option C

4. Quick Check:

   true && false = False [OK]

Hint: AND is true only if both are true [OK]

Common Mistakes:

• Thinking true && false is true
• Confusing AND with OR
• Expecting numeric output like 1 or 0

4. Identify the error in this C# code snippet:

bool isReady = True;
if(isReady)
{
    Console.WriteLine("Ready!");
}

medium

A. Missing semicolon after if statement

B. Boolean value should be lowercase true

C. Console.WriteLine syntax is incorrect

D. Variable name cannot be 'isReady'

Solution

1. Step 1: Check Boolean value capitalization

   In C#, Boolean literals are lowercase: true and false. True with uppercase T is invalid.

2. Step 2: Verify other parts of code

   Semicolon is present after variable declaration. Console.WriteLine syntax is correct. Variable name 'isReady' is valid.

3. Final Answer:

   Boolean value should be lowercase true -> Option B

4. Quick Check:

   Boolean literals are lowercase true/false [OK]

Hint: Boolean literals are always lowercase true or false [OK]

Common Mistakes:

• Using uppercase True or False
• Thinking semicolon is missing after if
• Assuming variable names are restricted

5. You want to write a C# program that prints "Access granted" only if a user is logged in and has admin rights. Which Boolean expression correctly checks this?

bool isLoggedIn = true;
bool isAdmin = false;
// Which condition to use in if?

hard

A. if (isLoggedIn && isAdmin)

B. if (isLoggedIn || isAdmin)

C. if (!isLoggedIn && isAdmin)

D. if (!isLoggedIn || !isAdmin)

Solution

1. Step 1: Understand the requirement

   The program should print "Access granted" only if the user is logged in AND has admin rights.

2. Step 2: Choose the correct Boolean operator

   AND operator && ensures both conditions are true. OR || would allow access if either is true, which is incorrect.

3. Final Answer:

   if (isLoggedIn && isAdmin) -> Option A

4. Quick Check:

   Use AND to require both conditions true [OK]

Hint: Use && to require both conditions true simultaneously [OK]

Common Mistakes:

• Using OR instead of AND
• Negating conditions incorrectly
• Confusing ! (not) operator usage