Finally block behavior in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of try-finally without catch

What is the output of this C# code snippet?

C Sharp (C#)

using System;
class Program {
  static void Main() {
    try {
      Console.WriteLine("Start");
    } finally {
      Console.WriteLine("Finally block executed");
    }
  }
}

A Finally block executed\nStart

B No output

C Start\nFinally block executed

D Start

💡 Hint

Remember that the finally block always runs after the try block, even if no exception occurs.

The try block runs first and prints "Start". Then the finally block runs and prints "Finally block executed". So both lines appear in order.

❓ Predict Output

intermediate

Finally block with exception thrown

What will be printed when this code runs?

C Sharp (C#)

using System;
class Program {
  static void Main() {
    try {
      Console.WriteLine("Before exception");
      throw new Exception("Error");
    } finally {
      Console.WriteLine("In finally");
    }
  }
}

A Before exception\nIn finally\nUnhandled Exception: Error

B In finally\nBefore exception\nUnhandled Exception: Error

C Before exception\nUnhandled Exception: Error

D No output

💡 Hint

The finally block runs even if an exception is thrown, before the exception propagates.

The try block prints "Before exception" then throws. The finally block runs and prints "In finally". Then the exception is unhandled and shown.

❓ Predict Output

advanced

Return value with finally modifying variable

What is the output of this program?

C Sharp (C#)

using System;
class Program {
  static int Test() {
    int x = 1;
    try {
      return x;
    } finally {
      x = 2;
      Console.WriteLine("Finally executed");
    }
  }
  static void Main() {
    Console.WriteLine(Test());
  }
}

A Finally executed\n1

B Finally executed\n2

C 1\nFinally executed

D 2\nFinally executed

💡 Hint

The return value is determined before finally runs, even if finally changes the variable.

The method returns x which is 1. The finally block runs and prints "Finally executed" but does not change the returned value.

❓ Predict Output

advanced

Finally block with return inside it

What will this program print?

C Sharp (C#)

using System;
class Program {
  static int Test() {
    try {
      return 1;
    } finally {
      return 2;
    }
  }
  static void Main() {
    Console.WriteLine(Test());
  }
}

A Runtime exception

B 1

C Compilation error

D 2

💡 Hint

A return in finally overrides any previous return from try.

The finally block's return replaces the try block's return, so the method returns 2.

🧠 Conceptual

expert

Behavior of finally with exception and return

Consider this code snippet. What happens when it runs?

C Sharp (C#)

using System;
class Program {
  static int Test() {
    try {
      throw new Exception("Error");
    } finally {
      return 42;
    }
  }
  static void Main() {
    Console.WriteLine(Test());
  }
}

A Prints nothing and program crashes

B Prints 42 and suppresses the exception

C Throws the exception and does not print anything

D Compilation error due to return in finally

💡 Hint

A return in finally block suppresses any exception thrown in try.

The exception is thrown but the finally block returns 42, which overrides the exception. So 42 is printed and no exception propagates.

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