Logical patterns (and, or, not) in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if both conditions are true.

C Sharp (C#)

bool result = (a > 5) [1] (b < 10);

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

A||

Bor

C|

D&&

Attempts:

3 left

💡 Hint

Common Mistakes

Using || instead of &&

Using single & which is a bitwise operator

The && operator checks if both conditions are true.

2fill in blank

medium

Complete the code to check if either condition is true.

C Sharp (C#)

bool result = (x == 0) [1] (y == 1);

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

A&

B||

C&&

Dand

Attempts:

3 left

💡 Hint

Common Mistakes

Using && instead of ||

Using single & which is a bitwise operator

The || operator checks if at least one condition is true.

3fill in blank

hard

Fix the error in the code to negate the condition.

C Sharp (C#)

bool isFalse = [1](flag);

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

A!

Bnot

C~

Dnegate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'not' keyword which is not valid in C#

Using bitwise complement operator ~ which is for integers

The ! operator negates a boolean value in C#.

4fill in blank

hard

Fill all three blanks to check if number is between 10 and 20 inclusive.

C Sharp (C#)

bool inRange = (num [1] 10) [2] (num [3] 20);

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

A>=

B&&

C<=

D||

Attempts:

3 left

💡 Hint

Common Mistakes

Using || instead of && which allows numbers outside the range

Using > or < instead of >= or <=

The code checks if num is greater than or equal to 10 and less than or equal to 20 using &&.

5fill in blank

hard

Fill all three blanks to check if a character is a vowel (a, e, i, o, u).

C Sharp (C#)

bool isVowel = (ch == 'a') [1] (ch == 'e') [2] (ch == 'i') [3] (ch == 'o') || (ch == 'u');

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

A||

B&&

Attempts:

3 left

💡 Hint

Common Mistakes

Using && which requires all conditions to be true (impossible here)

Mixing && and || operators incorrectly

Use || to check if ch equals any vowel character.

Practice

1.

Which logical operator in C# means both conditions must be true?

and, or, or not?

easy

A. and

B. or

C. not

D. xor

Solution

1. Step 1: Understand the meaning of logical operators

   The and operator requires both conditions to be true for the whole expression to be true.

2. Step 2: Compare with other operators

   or means one or both conditions are true, not negates a condition, and xor means exactly one condition is true.

3. Final Answer:

   and -> Option A

4. Quick Check:

   and means both true [OK]

Hint: Remember: and = both true, or = any true, not = reverse [OK]

Common Mistakes:

• Confusing 'and' with 'or'
• Thinking 'not' means both true
• Mixing 'xor' with 'and'

2.

Which of these is the correct C# syntax for the logical NOT operator?

?

easy

A. not x

B. x!

C. !x

D. ~x

Solution

1. Step 1: Recall C# logical NOT syntax

   In C#, the logical NOT operator is ! placed before the variable or expression.

2. Step 2: Check other options

   not x is not valid C# syntax, ~x is bitwise NOT, and x! is invalid.

3. Final Answer:

   !x -> Option C

4. Quick Check:

   Logical NOT uses ! before expression [OK]

Hint: Logical NOT is always ! before the variable [OK]

Common Mistakes:

• Using 'not' keyword instead of !
• Confusing bitwise ~ with logical !
• Placing ! after the variable

3.

What is the output of this C# code?

bool a = true;
bool b = false;
if (a && !b) {
    Console.WriteLine("Yes");
} else {
    Console.WriteLine("No");
}

medium

A. No

B. Yes

C. True

D. False

Solution

1. Step 1: Evaluate variables and conditions

   Variable a is true, b is false, so !b is true.

2. Step 2: Evaluate the if condition

   a && !b becomes true && true, which is true, so the if block runs.

3. Final Answer:

   Yes -> Option B

4. Quick Check:

   true and not false = true [OK]

Hint: Remember ! reverses boolean, so !false = true [OK]

Common Mistakes:

• Ignoring the ! operator
• Thinking false && true is true
• Confusing output strings with boolean values

4.

Find the error in this C# code snippet:

bool x = true;
if (x && !x) {
    Console.WriteLine("True");
} else {
    Console.WriteLine("False");
}

medium

A. Using single & instead of &&

B. Missing semicolon after if statement

C. Incorrect use of Console.WriteLine

D. Contradictory condition: x and not x can never be true

Solution

1. Step 1: Analyze the condition logic

   The condition x && !x means x is true AND x is false at the same time, which is impossible.

2. Step 2: Check syntax correctness

   The syntax is correct: && is used properly, semicolons and Console.WriteLine are fine.

3. Final Answer:

   Contradictory condition: x and not x can never be true -> Option D

4. Quick Check:

   True and not true = false always [OK]

Hint: Check if condition can ever be true logically [OK]

Common Mistakes:

• Thinking condition can be true
• Confusing & with &&
• Looking for syntax errors when logic is the issue

5.

You want to write a C# switch expression that returns "Valid" only if age is between 18 and 30 inclusive, and hasID is true. Which pattern correctly uses logical operators?

return (age, hasID) switch {
    ??? => "Valid",
    _ => "Invalid"
};

hard

A. var (a, id) when a >= 18 && a <= 30 && id

B. (>= 18 and <= 30 and true, hasID)

C. var a when a >= 18 && a <= 30 && hasID == true

D. (>= 18 and <= 30, true)

Solution

1. Step 1: Understand switch pattern matching with tuples

   The switch matches a tuple (age, hasID). To check conditions on both, use a when clause with logical operators.

2. Step 2: Analyze each option

   var (a, id) when a >= 18 && a <= 30 && id correctly uses tuple deconstruction var (a, id) and checks a >= 18 && a <= 30 && id (where id is boolean). Others are invalid syntax or misuse logical operators.

3. Final Answer:

   var (a, id) when a >= 18 && a <= 30 && id -> Option A

4. Quick Check:

   Tuple pattern with when and && is correct [OK]

Hint: Use tuple deconstruction with when and && for multiple conditions [OK]

Common Mistakes:

• Trying to use and inside tuple without when
• Misplacing logical operators outside when clause
• Not deconstructing tuple properly