Why operators matter in C Sharp (C#) - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add two numbers and print the result.

C Sharp (C#)

int a = 5;
int b = 3;
int sum = a [1] b;
Console.WriteLine(sum);

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

A+

B-

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction instead of addition.

Using multiplication or division by mistake.

The plus operator + adds two numbers together.

2fill in blank

medium

Complete the code to check if a number is greater than 10.

C Sharp (C#)

int number = 15;
if (number [1] 10)
{
    Console.WriteLine("Greater than 10");
}

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

A<=

B==

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using less than operator instead.

Using equality operator instead of comparison.

The greater than operator > checks if the left value is bigger than the right.

3fill in blank

hard

Fix the error in the code to multiply two numbers.

C Sharp (C#)

int x = 4;
int y = 6;
int product = x [1] y;
Console.WriteLine(product);

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

A/

B*

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition or subtraction instead of multiplication.

Using division operator by mistake.

The multiplication operator * multiplies two numbers.

4fill in blank

hard

Fill both blanks to create a dictionary with word lengths for words longer than 3 letters.

C Sharp (C#)

var words = new List<string> { "apple", "cat", "banana", "dog" };
var lengths = words.Where(word => word.Length [1] 3)
                   .ToDictionary(word => word, word => word.Length [2] 1);

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

A>

B<

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using less than operator for filtering.

Adding instead of subtracting in the dictionary value.

The first blank uses > to filter words longer than 3 letters.

The second blank uses - to subtract 1 from the length.

5fill in blank

hard

Fill all three blanks to create a dictionary with uppercase keys and their lengths for words with length greater than 4.

C Sharp (C#)

var words = new List<string> { "tree", "house", "car", "elephant" };
var result = words.Where(w => w.Length [1] 4)
                  .ToDictionary(w => w.[2](), w => w.Length [3] 0);

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

A>

BLength

C+

DToUpper

Attempts:

3 left

💡 Hint

Common Mistakes

Using less than operator for filtering.

Using property name instead of method call for uppercase.

Using subtraction instead of addition in length calculation.

The first blank uses > to filter words longer than 4 letters.

The second blank uses ToUpper to make keys uppercase.

The third blank uses + to add 0 to the length (keeps length unchanged).

Practice

1. What does the == operator do in C#?

easy

A. Checks if two values are equal

B. Assigns a value to a variable

C. Adds two numbers

D. Checks if two values are not equal

Solution

1. Step 1: Understand the purpose of ==

   The == operator compares two values to see if they are the same.

2. Step 2: Differentiate from other operators

   Unlike = which assigns, == checks equality.

3. Final Answer:

   Checks if two values are equal -> Option A

4. Quick Check:

   == means equality check [OK]

Hint: Remember: double equals means compare, single equals means assign [OK]

Common Mistakes:

• Confusing == with =
• Thinking == assigns values
• Mixing up equality and inequality operators

2. Which of the following is the correct syntax to add two integers a and b in C#?

easy

A. int sum = a - b;

B. int sum = a * b;

C. int sum = a + b;

D. int sum = a / b;

Solution

1. Step 1: Identify the addition operator

   The plus sign + is used to add two numbers in C#.

2. Step 2: Check the syntax correctness

   int sum = a + b; correctly declares an integer and assigns the sum.

3. Final Answer:

   int sum = a + b; -> Option C

4. Quick Check:

   Addition uses + operator [OK]

Hint: Use + to add numbers, not -, *, or / [OK]

Common Mistakes:

• Using subtraction - instead of addition
• Confusing multiplication or division for addition
• Missing semicolon at the end

3. What is the output of this C# code?

int x = 5;
int y = 10;
bool result = x > y || y == 10;
Console.WriteLine(result);

medium

A. True

B. 5

C. False

D. 10

Solution

1. Step 1: Evaluate the first condition x > y

   Since 5 is not greater than 10, this is false.

2. Step 2: Evaluate the second condition y == 10

   Since 10 equals 10, this is true.

3. Step 3: Apply the OR operator ||

   OR returns true if either side is true, so overall result is true.

4. Final Answer:

   True -> Option A

5. Quick Check:

   false || true = true [OK]

Hint: OR || is true if any side is true [OK]

Common Mistakes:

• Thinking both sides must be true for OR
• Confusing || with &&
• Misreading comparison operators

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

int a = 7;
int b = 3;
if (a = b) {
    Console.WriteLine("Equal");
} else {
    Console.WriteLine("Not Equal");
}

medium

A. Console.WriteLine syntax is wrong

B. Missing semicolon after if statement

C. Incorrect variable declaration

D. Using assignment = instead of comparison == in the if condition

Solution

1. Step 1: Identify the if condition error

   The condition uses = which assigns b to a, not compare.

2. Step 2: Correct operator usage

   Use == to compare values in conditions.

3. Final Answer:

   Using assignment = instead of comparison == in the if condition -> Option D

4. Quick Check:

   Use == for comparisons, not = [OK]

Hint: Use double equals == to compare in if statements [OK]

Common Mistakes:

• Using single equals = in conditions
• Thinking assignment works as comparison
• Ignoring compiler error messages

5. You want to check if a number n is between 10 and 20 inclusive in C#. Which operator combination correctly does this?

hard

A. if (n > 10 || n < 20)

B. if (n >= 10 && n <= 20)

C. if (n == 10 && n == 20)

D. if (n >= 10 || n <= 20)

Solution

1. Step 1: Understand the range condition

   We want n to be at least 10 and at most 20, so both conditions must be true.

2. Step 2: Use AND operator && to combine conditions

   Using n >= 10 && n <= 20 ensures n is between 10 and 20 inclusive.

3. Final Answer:

   if (n >= 10 && n <= 20) -> Option B

4. Quick Check:

   AND && means both conditions true [OK]

Hint: Use AND && to check both limits together [OK]

Common Mistakes:

• Using OR || which allows values outside range
• Using equality instead of range checks
• Confusing inclusive and exclusive operators