Assignment and compound assignment in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign the value 10 to the variable number.

C Sharp (C#)

int number [1] 10;

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

A=

B==

C+=

D=>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '=' causes a syntax error.

Using '+=' without initializing the variable first.

The single equal sign = is used to assign a value to a variable in C#.

2fill in blank

medium

Complete the code to add 5 to the variable score using a compound assignment operator.

C Sharp (C#)

score [1] 5;

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

A*=

B+=

C-=

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' only replaces the value instead of adding.

Using '-=' subtracts instead of adding.

The += operator adds the right value to the variable and assigns the result back to it.

3fill in blank

hard

Fix the error in the code to multiply count by 3 using a compound assignment.

C Sharp (C#)

count [1] 3;

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

A*=

B==

C=

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*' alone causes a syntax error.

Using '=' only assigns without multiplying.

The *= operator multiplies the variable by the value and assigns the result back to it.

4fill in blank

hard

Complete the code: first initialize value to 2, then subtract 2 from it using a compound assignment operator.

C Sharp (C#)

value [1] 2;
value [2] 2;

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

A-=

B=

C+=

D*=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+=' instead of '-=' for subtraction.

Using '=' for both lines causes no subtraction.

First, we assign the value 2 to value using =. Then, we subtract 2 from value using the compound assignment -=.

5fill in blank

hard

Fill all three blanks to add each word to the dictionary `lengths` mapping it to its length, but only if the length is greater than 3. Assume `word` is a string variable in scope.

C Sharp (C#)

var lengths = new Dictionary<string, int>();
if ([1] > 3) {
    lengths[[2]] = [3];
}

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

A"word"

B"word".Length

Cword.Length

Dword

Attempts:

3 left

💡 Hint

Common Mistakes

Using quoted strings instead of the variable word for keys.

Forgetting to use word.Length and using a string literal.

Check if word.Length > 3. If so, set lengths[word] = word.Length.

Practice

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

easy

A. Multiplies the left variable by the right value

B. Subtracts the right value from the left variable

C. Adds the right value to the left variable and assigns the result to the left variable

D. Divides the left variable by the right value

Solution

1. Step 1: Understand the operator meaning

   The += operator adds the right side value to the left side variable.

2. Step 2: Assign the result back

   The result of the addition is stored back into the left variable.

3. Final Answer:

   Adds the right value to the left variable and assigns the result to the left variable -> Option C

4. Quick Check:

   += means add and assign [OK]

Hint: Remember: += means add then assign in one step [OK]

Common Mistakes:

• Confusing += with subtraction or multiplication
• Thinking += just adds without assignment
• Using += on constants (which is invalid)

2. Which of the following is the correct syntax to multiply a variable x by 5 using a compound assignment in C#?

easy

A. x *= 5;

B. x =* 5;

C. x = *5;

D. x = x *=

Solution

1. Step 1: Identify correct compound assignment syntax

   The correct syntax for multiplication assignment is x *= 5; with no spaces between * and =.

2. Step 2: Check other options for syntax errors

   Options B, C, and D have invalid syntax or misplaced operators.

3. Final Answer:

   x *= 5; -> Option A

4. Quick Check:

   Use *= for multiply and assign [OK]

Hint: Compound operators combine symbol and = without spaces [OK]

Common Mistakes:

• Writing =* instead of *=
• Adding spaces between * and =
• Using incomplete or invalid syntax

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

int a = 10;
a += 5;
a -= 3;
Console.WriteLine(a);

medium

A. 12

B. 15

C. 8

D. 10

Solution

1. Step 1: Apply the first compound assignment

   Starting with a = 10, a += 5 adds 5, so a = 15.

2. Step 2: Apply the second compound assignment

   Then a -= 3 subtracts 3, so a = 12.

3. Final Answer:

   12 -> Option A

4. Quick Check:

   10 + 5 - 3 = 12 [OK]

Hint: Follow each compound step in order to find final value [OK]

Common Mistakes:

• Adding and subtracting in wrong order
• Confusing += and -= effects
• Forgetting to update variable after each step

4. Identify the error in the following code snippet:

int count = 5;
count + = 3;
Console.WriteLine(count);

medium

A. The variable count is not initialized

B. The code will output 8 without errors

C. Console.WriteLine is missing parentheses

D. The compound assignment operator has a space and is invalid

Solution

1. Step 1: Check variable initialization

   The variable count is correctly initialized to 5, so no error here.

2. Step 2: Examine the compound assignment syntax

   The code uses count + = 3; which has a space between + and =, making it invalid syntax. It should be count += 3;.

3. Final Answer:

   The compound assignment operator has a space and is invalid -> Option D

4. Quick Check:

   No spaces in compound operators like += [OK]

Hint: Compound operators must be written without spaces [OK]

Common Mistakes:

• Adding spaces between operator and =
• Assuming code runs despite syntax errors
• Confusing initialization errors with syntax errors

5. Given the code below, what will be the value of result after execution?

int x = 4;
int y = 3;
int result = 10;
result += x * y;
result -= y + 2;
result *= 2;

hard

A. 30

B. 34

C. 26

D. 28

Solution

1. Step 1: Calculate result += x * y

   Multiply x * y = 4 * 3 = 12. Add to result = 10 + 12 = 22.

2. Step 2: Calculate result -= y + 2

   Add y + 2 = 3 + 2 = 5. Subtract from result = 22 - 5 = 17.

3. Step 3: Calculate result *= 2

   Multiply result = 17 * 2 = 34.

4. Final Answer:

   34 -> Option B

5. Quick Check:

   10 + 12 - 5 = 17; 17 * 2 = 34 [OK]

Hint: Perform operations step-by-step respecting operator precedence [OK]

Common Mistakes:

• Ignoring multiplication precedence in compound assignment
• Calculating additions/subtractions in wrong order
• Forgetting to update result after each step