Switch statement execution in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of switch with fall-through using goto case

What is the output of this C# code snippet?

C Sharp (C#)

int x = 2;
switch (x)
{
    case 1:
        Console.WriteLine("One");
        break;
    case 2:
        Console.WriteLine("Two");
        goto case 3;
    case 3:
        Console.WriteLine("Three");
        break;
    default:
        Console.WriteLine("Default");
        break;
}

A Two\nThree

B Two

C Three

D Default

💡 Hint

Remember that 'goto case' transfers control to another case label.

When x is 2, it prints "Two" then jumps to case 3 and prints "Three" before breaking.

❓ Predict Output

intermediate

Switch expression output with pattern matching

What is the output of this C# code using a switch expression?

C Sharp (C#)

object obj = 5;
string result = obj switch
{
    int i when i > 0 => "Positive integer",
    int i when i < 0 => "Negative integer",
    string s => "String",
    _ => "Other"
};
Console.WriteLine(result);

A Positive integer

B Negative integer

C String

D Other

💡 Hint

Check the type and condition matched in the switch expression.

The object is an int with value 5, which is greater than 0, so it matches the first pattern.

🔧 Debug

advanced

Identify the error in switch statement

What error does this C# code produce?

C Sharp (C#)

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

A Runtime error: fall-through not allowed

B Compile-time error: duplicate case labels

C No error, output is Monday\nTuesday

D Compile-time error: missing break in case 1

💡 Hint

C# does not allow implicit fall-through between cases.

C# requires each case to end with break or other jump statement unless it ends with a goto or return. Missing break causes compile error.

❓ Predict Output

advanced

Switch with multiple case labels and default

What is the output of this C# switch statement?

C Sharp (C#)

char grade = 'B';
switch (grade)
{
    case 'A':
    case 'B':
        Console.WriteLine("Pass");
        break;
    case 'C':
        Console.WriteLine("Average");
        break;
    default:
        Console.WriteLine("Fail");
        break;
}

A Average

B Fail

C Pass

D No output

💡 Hint

Multiple case labels can share the same code block.

Grade 'B' matches case 'B', which shares code with case 'A', printing "Pass".

🧠 Conceptual

expert

Switch statement behavior with nullable types

Given the following code, what is the output?

C Sharp (C#)

int? number = null;
switch (number)
{
    case null:
        Console.WriteLine("Null value");
        break;
    case > 0:
        Console.WriteLine("Positive number");
        break;
    default:
        Console.WriteLine("Other number");
        break;
}

A Compile-time error

B Null value

C Other number

D Positive number

💡 Hint

Switch supports pattern matching including null checks on nullable types.

The nullable int is null, so it matches the 'case null' pattern and prints "Null value".

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