C# Exception Hierarchy Overview

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Questions and Answers

What will happen if either num1 or num2 is equal to zero when btnCompute_Click is executed?

A DivideByZeroException will be thrown. (correct)

The input fields will be cleared.

The application will crash.

The program will display the total of num1 and num2.

What type of exception does the catch block handle if the input is not in the correct format?

OverflowException

ArgumentNullException

FormatException (correct)

IndexOutOfRangeException

Which method is called to calculate the quotient of two integers?

GetAverage

CalculateDivision

GetSum

GetQuotient (correct)

How does the program inform the user of the random error that occurred in the catch blocks?

By writing to the console. Signup and view all the answers

What is necessary to create a custom exception in the .NET Framework?

Inherit from System.Exception or its derived classes. Signup and view all the answers

What type of exception is generated by user programs?

ApplicationException Signup and view all the answers

Which exception is thrown when there is an attempt to access an array index that is out of bounds?

System.IndexOutOfRangeException Signup and view all the answers

What C# keyword is used for executing a block of code regardless of whether an exception occurs?

finally Signup and view all the answers

Which exception is thrown when an arithmetic overflow occurs in a checked operation?

System.OverflowException Signup and view all the answers

What will happen if an exception is thrown within a try block?

It must be caught by a catch block Signup and view all the answers

Which exception indicates that a method received an invalid argument?

System.ArgumentException Signup and view all the answers

Which of the following exceptions is thrown when there is insufficient memory available?

System.OutOfMemoryException Signup and view all the answers

What occurs in the case of an exception when using a finally block?

It executes after the try and catch blocks, regardless of the outcome. Signup and view all the answers

What happens if an exception is thrown without a try-catch block?

An error message is displayed, and the application closes. Signup and view all the answers

What is required to create a new instance of an exception?

The 'new' operator must be used. Signup and view all the answers

Which of the following conditions will trigger the DivideByZeroException in the provided code?

When either num1 or num2 is equal to 0. Signup and view all the answers

What would be the result of the GetQuotient method if called with values 10 and 0?

Throws a DivideByZeroException. Signup and view all the answers

What will happen in the btnCompute_Click method if both text inputs are valid integers greater than 0?

The quotient will be displayed in a message box. Signup and view all the answers

What is the base class for the custom exception class in the provided example?

Exception Signup and view all the answers

What is the purpose of the constructor in the custom exception class?

To pass a message to the base class Signup and view all the answers

Which keyword is used to manually throw an exception in the provided code example?

throw Signup and view all the answers

In the context provided, what is the purpose of the finally block?

To execute cleanup code after a try-catch block. Signup and view all the answers

What will happen if the age passed to checkAge method is less than 18?

An InvalidUserInputException will be thrown Signup and view all the answers

What will happen if the input for num1 is 'abc' in the btnCompute_Click method?

The program will throw a format exception. Signup and view all the answers

Which method handles the exception thrown by checkAge?

btnCheck_Click Signup and view all the answers

Which statement correctly identifies the purpose of InvalidUserInputException?

It acts like a standard exception for invalid age input. Signup and view all the answers

What will the catch block in btnCheck_Click output if an InvalidUserInputException is thrown?

Message: Not in legal age! Signup and view all the answers

What is the function of the line 'throw new InvalidUserInputException("Not in legal age!");'?

To indicate the age check failed Signup and view all the answers

Where is the checkAge method invoked in the code sample?

In the btnCheck_Click method when the button is clicked Signup and view all the answers

Study Notes

The Exception Hierarchy

Exceptions in C# are represented by classes.
All exceptions are subclasses of the System.Exception class.
There are two types of exceptions.
- ApplicationException: generated by user programs.
- SystemException: generated by the Common Language Runtime (CLR).

Common Exceptions

System.Exception: the root of the exception hierarchy.
System.ArithmeticException: thrown when an arithmetic or conversion operation encounters an error.
System.OverflowException: thrown when a checked operation overflows.
System.ArgumentException: thrown when a method receives an invalid argument.
System.ArgumentNullException: thrown when a method receives a null argument.
System.IndexOutOfRangeException: thrown when an array is indexed with an invalid index.
System.OutOfMemoryException: thrown when the available memory is insufficient.
System.StackOverflowException: thrown when the execution stack is exhausted due to too many pending method calls.
System.FormatException: thrown when a string or argument fails to meet a specific format.

The `try-catch` Block

The try-catch block is used for handling exceptions in C#.
It involves four keywords:
- try: encloses the code to be checked for exceptions.
- catch: catches the exception thrown in the try block.
- throw: used to manually throw an exception.
- finally: executes a statement regardless of whether an exception is thrown or not.

Manually Throwing an Exception

Exceptions can be thrown manually using the throw keyword.
Syntax: throw new exception_object;
exception_object is an instance of a class derived from Exception.
new operator creates a new object of the exception class.

Custom Exceptions

You can create your own custom exception classes in C#.
Custom exception classes must inherit from System.Exception or one of its derived classes.
Custom exceptions can be thrown and handled like standard exceptions.

Example: Custom Exception Class

Example custom exception class InvalidUserInputException:
```
public class InvalidUserInputException : Exception
{
    public InvalidUserInputException(string age) : base(age)
    {
    }
}
```
- This custom exception can be used to indicate invalid user input, for example, age that is not valid.
- The constructor takes a string argument (age) representing a message describing the invalid input.
- The custom exception class can be used like any other exception:
  - Throw: throw new InvalidUserInputException("Not in legal age!");
  - Catch: catch(InvalidUserInputException ex) { ... }

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Description

This quiz covers the C# exception hierarchy, focusing on the classification and purpose of various exceptions. Learn about the root exception class, common exceptions like System.ArgumentException and System.OverflowException, and their specific uses in application development.