Finally block behavior in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to ensure the finally block always executes.

C Sharp (C#)

try {
    Console.WriteLine("Try block");
} [1] {
    Console.WriteLine("Finally block");
}

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

Aelse

Bcatch

Cwhen

Dfinally

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'catch' instead of 'finally' causes the block to run only on exceptions.

Using 'else' or 'when' are invalid here.

The finally block always runs after the try block, regardless of exceptions.

2fill in blank

medium

Complete the code to catch exceptions and still run the finally block.

C Sharp (C#)

try {
    int x = 5 / 0;
} [1] (DivideByZeroException ex) {
    Console.WriteLine("Caught exception");
} finally {
    Console.WriteLine("Always runs");
}

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

Ausing

Bfinally

Ccatch

Dthrow

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'finally' instead of 'catch' to handle exceptions.

Using 'throw' or 'using' here is incorrect.

The catch block handles exceptions, and the finally block runs after that.

3fill in blank

hard

Fix the error in the code to ensure the finally block runs after the try-catch.

C Sharp (C#)

try {
    Console.WriteLine("Start");
} catch (Exception ex) {
    Console.WriteLine("Error");
} [1] {
    Console.WriteLine("Cleanup");
}

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

Afinally

Bcatch

Cthrow

Delse

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'catch' again instead of 'finally'.

Using 'throw' or 'else' causes syntax errors.

The finally block must be used to run code after try-catch regardless of exceptions.

4fill in blank

hard

Fill both blanks to complete the try-catch-finally structure correctly.

C Sharp (C#)

try {
    int[] arr = new int[2];
    Console.WriteLine(arr[3]);
} [1] (IndexOutOfRangeException ex) {
    Console.WriteLine("Index error");
} [2] {
    Console.WriteLine("Always runs");
}

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

Acatch

Bfinally

Cthrow

Dusing

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping 'catch' and 'finally' keywords.

Using 'throw' or 'using' in these positions.

The catch block handles the exception, and finally runs always after try-catch.

5fill in blank

hard

Fill all three blanks to create a try-catch-finally that throws and cleans up properly.

C Sharp (C#)

try {
    Console.WriteLine("Start");
    throw new Exception("Error");
} [1] (Exception ex) {
    Console.WriteLine(ex.Message);
    [2];
} [3] {
    Console.WriteLine("Cleanup done");
}

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

Acatch

Bthrow

Cfinally

Dreturn

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting 'throw' causes the exception to be swallowed.

Using 'return' inside catch changes flow incorrectly.

Misplacing 'finally' block.

The catch block catches the exception, throw rethrows it, and finally runs cleanup code.

Practice

1. What is the main purpose of the finally block in C# exception handling?

easy

A. To execute code regardless of whether an exception occurs or not

B. To catch exceptions thrown in the try block

C. To declare variables used in the try block

D. To stop the program when an exception occurs

Solution

1. Step 1: Understand the role of finally

   The finally block runs after the try and catch blocks, no matter what happens.

2. Step 2: Identify its purpose

   It is used to run cleanup code or important steps that must always execute, regardless of exceptions.

3. Final Answer:

   To execute code regardless of whether an exception occurs or not -> Option A

4. Quick Check:

   finally always runs [OK]

Hint: Remember: finally always runs, no matter what [OK]

Common Mistakes:

• Confusing finally with catch block
• Thinking finally only runs on exceptions
• Believing finally can catch exceptions

2. Which of the following is the correct syntax for using a finally block in C#?

easy

A. try { } catch { } finally { }

B. try { } finally { } catch { }

C. try { } catch { }

D. finally { } try { } catch { }

Solution

1. Step 1: Recall correct order of blocks

   In C#, the order is try, then catch (optional), then finally (optional).

2. Step 2: Match syntax

   Only try { } catch { } finally { } shows the correct order: try { } catch { } finally { }.

3. Final Answer:

   try { } catch { } finally { } -> Option A

4. Quick Check:

   Correct block order [OK]

Hint: Remember order: try, catch, then finally [OK]

Common Mistakes:

• Placing finally before catch
• Omitting try block
• Using finally without try

3. What will be the output of the following C# code?

try {
    Console.WriteLine("Start");
    throw new Exception();
} catch {
    Console.WriteLine("Caught");
} finally {
    Console.WriteLine("Finally");
}

medium

A. Start\nFinally

B. Start\nCaught\nFinally

C. Caught\nFinally

D. Start\nCaught

Solution

1. Step 1: Trace the try block

   "Start" is printed, then an exception is thrown.

2. Step 2: Catch and finally execution

   The exception is caught, so "Caught" is printed, then the finally block runs printing "Finally".

3. Final Answer:

   Start\nCaught\nFinally -> Option B

4. Quick Check:

   try prints Start, catch prints Caught, finally prints Finally [OK]

Hint: Remember: finally runs after catch even if exception thrown [OK]

Common Mistakes:

• Ignoring catch block output
• Thinking finally runs before catch
• Missing the exception thrown in try

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

try {
    Console.WriteLine("Hello");
} finally {
    Console.WriteLine("Cleanup");
} catch (Exception ex) {
    Console.WriteLine("Error");
}

medium

A. The catch block must come after finally

B. No error, code is correct

C. You cannot use finally without catch

D. The finally block must come after catch

Solution

1. Step 1: Check block order rules

   In C#, the finally block must come after all catch blocks.

2. Step 2: Identify incorrect order

   The code places finally before catch, which is invalid syntax.

3. Final Answer:

   The finally block must come after catch -> Option D

4. Quick Check:

   finally after catch [OK]

Hint: Remember: catch blocks come before finally [OK]

Common Mistakes:

• Placing finally before catch
• Thinking finally can be before catch
• Confusing order of blocks

5. Consider this code:

int result = 0;
try {
    result = 10 / 0;
} catch (DivideByZeroException) {
    result = 1;
} finally {
    result = 2;
}
Console.WriteLine(result);

What will be printed and why?

hard

A. 0, because division by zero stops execution before catch

B. 1, because catch sets result to 1 and finally does not change it

C. 2, because finally always runs and can overwrite result

D. Exception thrown, program crashes

Solution

1. Step 1: Analyze exception and catch block

   Division by zero throws DivideByZeroException, caught by catch which sets result = 1.

2. Step 2: Understand finally block effect

   The finally block runs after catch and sets result = 2, overwriting previous value.

3. Final Answer:

   2, because finally always runs and can overwrite result -> Option C

4. Quick Check:

   finally runs last and sets result = 2 [OK]

Hint: finally runs last and can overwrite variables set earlier [OK]

Common Mistakes:

• Assuming catch value stays after finally
• Thinking exception stops finally from running
• Believing program crashes without output