Multiple catch blocks in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to catch a general exception.

C Sharp (C#)

try {
    int result = 10 / 0;
} catch ([1] e) {
    Console.WriteLine("Error occurred");
}

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

Astring

Bint

CException

Ddouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using a data type like int or string instead of Exception.

Missing the exception type in the catch block.

The Exception type is used to catch general exceptions in C#.

2fill in blank

medium

Complete the code to catch a specific exception type for division by zero.

C Sharp (C#)

try {
    int result = 10 / 0;
} catch ([1] e) {
    Console.WriteLine("Cannot divide by zero.");
}

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

AFormatException

BNullReferenceException

CIndexOutOfRangeException

DDivideByZeroException

Attempts:

3 left

💡 Hint

Common Mistakes

Using unrelated exception types like NullReferenceException.

Catching the wrong exception type.

The DivideByZeroException is thrown when division by zero occurs.

3fill in blank

hard

Fix the error in the catch block to catch multiple exceptions separately.

C Sharp (C#)

try {
    string text = null;
    Console.WriteLine(text.Length);
} catch ([1] e) {
    Console.WriteLine("Null reference error.");
} catch (Exception e) {
    Console.WriteLine("General error.");
}

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

AException

BNullReferenceException

CDivideByZeroException

DFormatException

Attempts:

3 left

💡 Hint

Common Mistakes

Using Exception in the first catch block instead of NullReferenceException.

Not ordering catch blocks from specific to general.

The NullReferenceException is used to catch errors when accessing members of a null object.

4fill in blank

hard

Fill both blanks to catch specific exceptions and a general exception.

C Sharp (C#)

try {
    int[] numbers = {1, 2, 3};
    Console.WriteLine(numbers[5]);
} catch ([1] e) {
    Console.WriteLine("Index error.");
} catch ([2] e) {
    Console.WriteLine("Other error.");
}

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

AIndexOutOfRangeException

BDivideByZeroException

CException

DNullReferenceException

Attempts:

3 left

💡 Hint

Common Mistakes

Reversing the order of catch blocks.

Using unrelated exception types.

The IndexOutOfRangeException catches errors when accessing invalid array indexes, and Exception catches all other errors.

5fill in blank

hard

Fill all three blanks to catch multiple exceptions and print their messages.

C Sharp (C#)

try {
    string input = null;
    int length = input.Length;
    int result = 10 / 0;
} catch ([1] e) {
    Console.WriteLine("Null error: " + e.Message);
} catch ([2] e) {
    Console.WriteLine("Divide error: " + e.Message);
} catch ([3] e) {
    Console.WriteLine("General error: " + e.Message);
}

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

ANullReferenceException

BDivideByZeroException

CException

DIndexOutOfRangeException

Attempts:

3 left

💡 Hint

Common Mistakes

Incorrect order of catch blocks.

Using wrong exception types for the errors.

Catch NullReferenceException first, then DivideByZeroException, and finally the general Exception.

Practice

1.

What is the main purpose of using multiple catch blocks in C#?

easy

A. To avoid using try blocks

B. To handle different types of exceptions separately

C. To make the code run faster

D. To declare multiple variables

Solution

1. Step 1: Understand the role of catch blocks

   catch blocks are used to handle errors that happen in the try block.

2. Step 2: Recognize why multiple catch blocks are used

   Using multiple catch blocks lets you respond differently to different error types, making your program clearer and safer.

3. Final Answer:

   To handle different types of exceptions separately -> Option B

4. Quick Check:

   Multiple catch blocks = handle different exceptions [OK]

Hint: Multiple catch blocks handle different errors separately [OK]

Common Mistakes:

• Thinking multiple catch blocks speed up code
• Believing catch blocks replace try blocks
• Using catch blocks to declare variables

2.

Which of the following is the correct syntax order for multiple catch blocks in C#?

try { ... }
catch (ArgumentNullException e) { ... }
catch (Exception e) { ... }

easy

A. Specific exceptions first, general exceptions last

B. General exceptions first, specific exceptions last

C. Order does not matter

D. Only one catch block is allowed

Solution

1. Step 1: Understand exception hierarchy

   Specific exceptions like ArgumentNullException inherit from general exceptions like Exception.

2. Step 2: Order catch blocks correctly

   Place specific exceptions first so they catch their errors before the general catch block handles all others.

3. Final Answer:

   Specific exceptions first, general exceptions last -> Option A

4. Quick Check:

   Specific before general catch blocks [OK]

Hint: Put specific exceptions before general ones in catch blocks [OK]

Common Mistakes:

• Placing general catch before specific causes unreachable code
• Assuming catch order does not matter
• Trying to use multiple catch blocks without try

3.

What will be the output of this C# code?

try {
    int[] arr = new int[2];
    Console.WriteLine(arr[5]);
} catch (IndexOutOfRangeException) {
    Console.WriteLine("Index error caught");
} catch (Exception) {
    Console.WriteLine("General error caught");
}

medium

A. No output, program crashes

B. General error caught

C. Index error caught

D. Compilation error

Solution

1. Step 1: Identify the exception thrown

   Accessing arr[5] causes an IndexOutOfRangeException because the array size is 2.

2. Step 2: Match exception to catch block

   The first catch block matches IndexOutOfRangeException, so it runs and prints "Index error caught".

3. Final Answer:

   Index error caught -> Option C

4. Quick Check:

   IndexOutOfRangeException triggers first catch [OK]

Hint: Exception type matches first suitable catch block [OK]

Common Mistakes:

• Thinking general catch runs before specific
• Assuming no exception occurs
• Confusing exception types

4.

Find the error in this code snippet:

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

medium

A. The FormatException catch block is unreachable

B. Missing finally block

C. Try block syntax is incorrect

D. No error, code is correct

Solution

1. Step 1: Check catch block order

   The first catch block catches all Exception types, including FormatException.

2. Step 2: Identify unreachable catch block

   Since Exception catch is first, the FormatException catch block can never run, causing a compile error.

3. Final Answer:

   The FormatException catch block is unreachable -> Option A

4. Quick Check:

   General catch before specific causes unreachable code [OK]

Hint: Place specific catch blocks before general ones to avoid unreachable code [OK]

Common Mistakes:

• Putting general catch before specific
• Ignoring unreachable code errors
• Thinking finally block is mandatory

5.

You want to handle NullReferenceException and DivideByZeroException differently, but also catch any other exceptions generally. Which is the best order of catch blocks?

try {
    // code that may throw exceptions
} catch (___) {
    Console.WriteLine("Null reference error");
} catch (___) {
    Console.WriteLine("Divide by zero error");
} catch (___) {
    Console.WriteLine("Other error");
}

hard

A. Exception, DivideByZeroException, NullReferenceException

B. Exception, NullReferenceException, DivideByZeroException

C. DivideByZeroException, Exception, NullReferenceException

D. NullReferenceException, DivideByZeroException, Exception

Solution

1. Step 1: Identify specific exceptions

   NullReferenceException and DivideByZeroException are specific exceptions to catch first.

2. Step 2: Place general exception last

   The general Exception catch block should come last to catch all other exceptions.

3. Final Answer:

   NullReferenceException, DivideByZeroException, Exception -> Option D

4. Quick Check:

   Specific exceptions first, general last [OK]

Hint: Catch specific exceptions before general Exception last [OK]

Common Mistakes:

• Putting Exception catch first
• Mixing order of specific exceptions
• Omitting general catch block