Try-catch execution flow in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of try-catch with exception thrown

What is the output of this C# code?

C Sharp (C#)

try {
    Console.WriteLine("Start");
    throw new Exception("Error");
    Console.WriteLine("End");
} catch (Exception ex) {
    Console.WriteLine("Caught: " + ex.Message);
}
Console.WriteLine("After try-catch");

A Start\nCaught: Error\nAfter try-catch

B Start\nEnd\nCaught: Error\nAfter try-catch

C Caught: Error\nAfter try-catch

D Start\nAfter try-catch

💡 Hint

Remember that code after the throw inside try is skipped.

The code prints "Start", then throws an exception. The line "End" is skipped. The catch block prints the exception message. Finally, the line after try-catch runs.

❓ Predict Output

intermediate

Output when no exception is thrown

What will this C# code print?

C Sharp (C#)

try {
    Console.WriteLine("Try block");
} catch {
    Console.WriteLine("Catch block");
} finally {
    Console.WriteLine("Finally block");
}

A Catch block\nFinally block

B Try block\nFinally block

C Try block\nCatch block\nFinally block

D Finally block

💡 Hint

No exception means catch block is skipped.

Since no exception occurs, the catch block is skipped. The finally block always runs.

❓ Predict Output

advanced

Exception in finally block

What is the output of this code?

C Sharp (C#)

try {
    Console.WriteLine("In try");
    throw new Exception("Try exception");
} catch (Exception ex) {
    Console.WriteLine("In catch: " + ex.Message);
} finally {
    Console.WriteLine("In finally");
    throw new Exception("Finally exception");
}
Console.WriteLine("After try-catch-finally");

A In try\nIn finally\nUnhandled exception: Finally exception

B In try\nIn catch: Try exception\nIn finally\nAfter try-catch-finally

C In try\nIn catch: Try exception\nIn finally\nUnhandled exception: Finally exception

D In try\nIn catch: Try exception\nAfter try-catch-finally

💡 Hint

Exception in finally overrides previous exception.

The try throws an exception caught by catch. Finally runs and throws a new exception, which is unhandled and stops execution.

❓ Predict Output

advanced

Return value with try-catch-finally

What value does this method return?

C Sharp (C#)

int Test() {
    try {
        return 1;
    } catch {
        return 2;
    } finally {
        return 3;
    }
}
Console.WriteLine(Test());

A 3

B 2

C 1

D 0

💡 Hint

Finally return overrides other returns.

The finally block's return overrides the try's return, so the method returns 3.

🧠 Conceptual

expert

Exception propagation with nested try-catch

Consider this code snippet. Which statement is true about the output?

C Sharp (C#)

try {
    try {
        throw new InvalidOperationException("Inner");
    } catch (ArgumentException) {
        Console.WriteLine("Caught ArgumentException");
    }
} catch (Exception ex) {
    Console.WriteLine("Caught Exception: " + ex.Message);
}

A Caught ArgumentException

B Caught Exception: ArgumentException

C No output, program crashes

D Caught Exception: Inner

💡 Hint

Inner catch only handles ArgumentException, not InvalidOperationException.

The inner catch does not catch InvalidOperationException, so it propagates to outer catch which prints the message.

Practice

1. What happens when an exception occurs inside a try block in C#?

easy

A. The program immediately jumps to the catch block to handle the error.

B. The program ignores the error and continues running the try block.

C. The program stops running without executing any further code.

D. The program restarts the try block from the beginning.

Solution

1. Step 1: Understand try-catch flow

   The try block runs code that might cause an error.

2. Step 2: Exception triggers catch block

   If an error happens, control moves to the catch block to handle it.

3. Final Answer:

   The program immediately jumps to the catch block to handle the error. -> Option A

4. Quick Check:

   Exception in try -> catch runs [OK]

Hint: Errors in try always jump to catch block [OK]

Common Mistakes:

• Thinking the program ignores errors in try
• Assuming the program restarts try block
• Believing the program stops without catch

2. Which of the following is the correct syntax to catch an exception in C#?

easy

A. try { /* code */ } catch (ex Exception) { /* handle */ }

B. try { /* code */ } catch Exception ex { /* handle */ }

C. try { /* code */ } catch { Exception ex } { /* handle */ }

D. try { /* code */ } catch (Exception ex) { /* handle */ }

Solution

1. Step 1: Recall correct catch syntax

   The catch block must have parentheses with exception type and variable: catch (Exception ex).

2. Step 2: Identify correct option

   Only try { /* code */ } catch (Exception ex) { /* handle */ } uses the correct syntax with parentheses and exception variable.

3. Final Answer:

   try { /* code */ } catch (Exception ex) { /* handle */ } -> Option D

4. Quick Check:

   Correct catch syntax = catch (Exception ex) [OK]

Hint: Catch needs parentheses with exception type and variable [OK]

Common Mistakes:

• Omitting parentheses around exception
• Swapping exception type and variable order
• Using braces instead of parentheses

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

try {
    Console.WriteLine("Start");
    int x = 5 / 0;
    Console.WriteLine("End");
} catch (DivideByZeroException) {
    Console.WriteLine("Error caught");
}

medium

A. Start\nError caught

B. Error caught

C. Start\nEnd

D. Start

Solution

1. Step 1: Trace code inside try block

   "Start" prints first. Then division by zero causes an exception.

2. Step 2: Exception triggers catch block

   Catch block runs and prints "Error caught". The line after division is skipped.

3. Final Answer:

   Start\nError caught -> Option A

4. Quick Check:

   Exception skips rest of try, catch prints message [OK]

Hint: Exception skips rest of try, catch runs next [OK]

Common Mistakes:

• Assuming 'End' prints after exception
• Thinking catch runs before 'Start'
• Ignoring exception and continuing try

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

try {
    int[] arr = new int[2];
    arr[3] = 10;
} catch (Exception e) {
    Console.WriteLine("Exception caught");
}

medium

A. Array index out of bounds exception is not caught.

B. The catch block syntax is incorrect.

C. The code will throw an exception but catch block handles it correctly.

D. The try block has a syntax error.

Solution

1. Step 1: Analyze the try block code

   Accessing index 3 in an array of size 2 causes an IndexOutOfRangeException.

2. Step 2: Check catch block handling

   Catch block catches all exceptions of type Exception, so it will handle this error and print the message.

3. Final Answer:

   The code will throw an exception but catch block handles it correctly. -> Option C

4. Quick Check:

   Exception thrown and caught properly [OK]

Hint: Catch(Exception e) catches all exceptions [OK]

Common Mistakes:

• Thinking catch syntax is wrong
• Assuming exception is not caught
• Believing try block has syntax error

5. Consider this code:

try {
    Console.WriteLine("A");
    try {
        int y = int.Parse("abc");
    } catch (FormatException) {
        Console.WriteLine("Format error");
    }
    Console.WriteLine("B");
} catch (Exception) {
    Console.WriteLine("General error");
}

What will be the output?

hard

A. A\nGeneral error\nB

B. A\nFormat error\nB

C. Format error\nB

D. A\nB

Solution

1. Step 1: Trace outer try block

   Prints "A" first, then enters inner try block.

2. Step 2: Inner try-catch handles FormatException

   Parsing "abc" causes FormatException, caught by inner catch which prints "Format error".

3. Step 3: Continue outer try after inner catch

   After inner catch, prints "B". Outer catch is not triggered.

4. Final Answer:

   A\nFormat error\nB -> Option B

5. Quick Check:

   Inner catch handles error, outer continues [OK]

Hint: Inner catch handles error, outer try continues after [OK]

Common Mistakes:

• Assuming outer catch runs instead of inner
• Thinking code stops after inner exception
• Missing that 'B' prints after inner catch