Switch statement execution in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of a switch statement in C#?

A switch statement allows you to choose between many options based on the value of a variable. It helps to run different code blocks depending on the value, making the code easier to read than many if-else statements.

beginner

How does the switch statement decide which case to execute?

The switch statement compares the value of the expression with each case label. When it finds a matching case, it executes the code inside that case until it hits a break or the end of the switch.

beginner

What happens if no case matches in a switch statement?

If no case matches, the code inside the default case runs if it exists. The default case acts like a fallback for any value not covered by other cases.

beginner

Why is the break statement important in a switch case?

The break statement stops the switch from running into the next case. Without break, the program continues executing the next cases, which can cause unexpected behavior.

intermediate

Can a switch statement in C# handle multiple cases with the same code?

Yes, you can list multiple case labels one after another without break statements between them. This way, all those cases run the same code block.

What keyword ends a case block in a C# switch statement to prevent fall-through?

A return

B continue

C break

D stop

The break keyword stops execution inside the switch and prevents running into the next case.

What happens if you omit the break statement in a switch case?

A The next case's code runs too

B The switch ends immediately

C The program throws an error

D The default case runs

Without break, execution continues into the next case, which is called fall-through.

Which case runs if no other case matches and a default case is present?

A The default case

B No case runs

C The last case

D The first case

The default case acts as a fallback when no other case matches.

Can a switch statement in C# use strings as case labels?

A No

B Yes

C Only with special syntax

D Only in newer versions

C# supports string values in switch case labels.

How do you group multiple cases to run the same code in a switch?

A Use if statements inside switch

B Use commas between case labels

C Use a special group keyword

D Write cases one after another without break

Listing cases consecutively without break groups them to run the same code.

Explain how a switch statement executes when given a value. Include what happens when a matching case is found and the role of break.

Think about how the program picks and runs one case among many.

Describe how you can handle multiple values with the same code block inside a switch statement.

Consider how to avoid repeating code for similar cases.

Practice

1.

What is the main purpose of a switch statement in C#?

easy

A. To repeat a block of code multiple times

B. To execute different code blocks based on the value of a variable

C. To define a function

D. To declare variables

Solution

1. Step 1: Understand the role of switch

   A switch statement selects one of many code blocks to execute based on a variable's value.

2. Step 2: Compare with other options

   Loops repeat code, functions define reusable code, and variable declarations create variables, none of which match switch's purpose.

3. Final Answer:

   To execute different code blocks based on the value of a variable -> Option B

4. Quick Check:

   Switch chooses code by value = A [OK]

Hint: Switch chooses code based on variable value [OK]

Common Mistakes:

• Confusing switch with loops
• Thinking switch defines functions
• Believing switch declares variables

2.

Which of the following is the correct syntax to start a switch statement in C#?

?

easy

A. switch (variable) { case 1: break; }

B. switch variable { case 1: break; }

C. switch (variable) case 1: break;

D. switch { variable case 1: break; }

Solution

1. Step 1: Recall switch syntax

   The correct syntax uses parentheses around the variable and braces around cases: switch (variable) { ... }

2. Step 2: Check each option

   switch (variable) { case 1: break; } matches correct syntax; others miss parentheses or braces or have wrong order.

3. Final Answer:

   switch (variable) { case 1: break; } -> Option A

4. Quick Check:

   Parentheses and braces required = C [OK]

Hint: Switch needs (variable) and { cases } syntax [OK]

Common Mistakes:

• Omitting parentheses around variable
• Missing braces around cases
• Incorrect order of keywords

3.

What will be the output of this C# code?

int day = 3;
switch (day) {
  case 1:
    Console.WriteLine("Monday");
    break;
  case 2:
    Console.WriteLine("Tuesday");
    break;
  case 3:
    Console.WriteLine("Wednesday");
    break;
  default:
    Console.WriteLine("Invalid day");
    break;
}

medium

A. Wednesday

B. Monday

C. Tuesday

D. Invalid day

Solution

1. Step 1: Identify the switch variable value

   The variable day is 3.

2. Step 2: Match case with variable

   Case 3 matches, so it prints "Wednesday" and then breaks.

3. Final Answer:

   Wednesday -> Option A

4. Quick Check:

   day=3 prints Wednesday [OK]

Hint: Match variable value to case label [OK]

Common Mistakes:

• Forgetting break causes fall-through
• Choosing default when case matches
• Mixing case numbers and output

4.

Find the error in this switch statement and select the fix:

int number = 2;
switch (number) {
  case 1:
    Console.WriteLine("One");
  case 2:
    Console.WriteLine("Two");
  default:
    Console.WriteLine("Default");
}

medium

A. Add semicolon after switch statement

B. Remove the default case

C. Change switch to if

D. Add break; after each case block

Solution

1. Step 1: Identify missing break statements

   Each case lacks a break, causing fall-through to next cases.

2. Step 2: Fix by adding breaks

   Adding break after each case stops fall-through and executes only matched case.

3. Final Answer:

   Add break; after each case block -> Option D

4. Quick Check:

   Break stops fall-through = A [OK]

Hint: Add break to stop fall-through in switch [OK]

Common Mistakes:

• Ignoring fall-through behavior
• Removing default case unnecessarily
• Misusing if instead of switch

5.

Given this code, what will be printed?

int score = 85;
switch (score / 10) {
  case 10:
  case 9:
    Console.WriteLine("Excellent");
    break;
  case 8:
    Console.WriteLine("Good");
    break;
  case 7:
  case 6:
    Console.WriteLine("Pass");
    break;
  default:
    Console.WriteLine("Fail");
    break;
}

hard

A. Excellent

B. Fail

C. Good

D. Pass

Solution

1. Step 1: Calculate switch expression value

   score is 85, so score / 10 is 8 (integer division).

2. Step 2: Match case for value 8

   Case 8 prints "Good" and breaks.

3. Final Answer:

   Good -> Option C

4. Quick Check:

   85/10=8 prints Good [OK]

Hint: Divide score by 10, match case labels [OK]

Common Mistakes:

• Not using integer division
• Missing combined cases for 9 and 10
• Choosing default incorrectly