Exception hierarchy in .NET in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this code snippet?

Consider the following C# code that catches exceptions:

try {
    throw new System.IO.FileNotFoundException("File missing");
} catch (System.Exception ex) {
    Console.WriteLine(ex.GetType().Name);
}

What will be printed?

C Sharp (C#)

try {
    throw new System.IO.FileNotFoundException("File missing");
} catch (System.Exception ex) {
    Console.WriteLine(ex.GetType().Name);
}

A FileNotFoundException

B SystemException

C Exception

D IOException

💡 Hint

FileNotFoundException inherits from IOException, which inherits from Exception.

The thrown exception is of type FileNotFoundException. The catch block catches it as Exception, but ex.GetType().Name returns the actual runtime type, which is FileNotFoundException.

❓ Predict Output

intermediate

What exception type is caught here?

Given this code snippet:

try {
    throw new System.ArgumentNullException("param");
} catch (System.SystemException ex) {
    Console.WriteLine(ex.GetType().Name);
}

What will be printed?

C Sharp (C#)

try {
    throw new System.ArgumentNullException("param");
} catch (System.SystemException ex) {
    Console.WriteLine(ex.GetType().Name);
}

A SystemException

B InvalidOperationException

C Exception

D ArgumentNullException

💡 Hint

ArgumentNullException inherits from SystemException.

The thrown exception is ArgumentNullException, which inherits from SystemException. The catch block catches SystemException, so it catches the thrown exception. The ex.GetType().Name returns the actual type ArgumentNullException.

❓ Predict Output

advanced

What error does this code raise?

Examine this code snippet:

try {
    throw new System.Exception("Error");
} catch (System.IO.IOException ex) {
    Console.WriteLine("IO error");
} catch (System.Exception ex) {
    Console.WriteLine("General error");
}

What will be printed?

C Sharp (C#)

try {
    throw new System.Exception("Error");
} catch (System.IO.IOException ex) {
    Console.WriteLine("IO error");
} catch (System.Exception ex) {
    Console.WriteLine("General error");
}

A General error

B IO error

C No output, program crashes

D Compilation error

💡 Hint

Exception is not an IOException, but it is an Exception.

The thrown exception is Exception. The first catch block for IOException does not match. The second catch block for Exception matches and prints General error.

❓ Predict Output

advanced

What is the output of this code with nested exceptions?

Look at this code:

try {
    try {
        throw new System.IndexOutOfRangeException("Index error");
    } catch (System.Exception ex) {
        throw new System.ApplicationException("App error", ex);
    }
} catch (System.ApplicationException ex) {
    Console.WriteLine(ex.InnerException.GetType().Name);
}

What will be printed?

C Sharp (C#)

try {
    try {
        throw new System.IndexOutOfRangeException("Index error");
    } catch (System.Exception ex) {
        throw new System.ApplicationException("App error", ex);
    }
} catch (System.ApplicationException ex) {
    Console.WriteLine(ex.InnerException.GetType().Name);
}

A Exception

B ApplicationException

C IndexOutOfRangeException

D NullReferenceException

💡 Hint

The inner exception is the original exception thrown inside the inner try block.

The inner try throws IndexOutOfRangeException. It is caught and wrapped inside an ApplicationException. The outer catch prints the type of the inner exception, which is IndexOutOfRangeException.

🧠 Conceptual

expert

Which exception type is the base for all CLR exceptions?

In the .NET exception hierarchy, which class is the ultimate base class for all exceptions thrown by the Common Language Runtime (CLR)?

A System.ApplicationException

B System.Exception

C System.SystemException

D System.Object

💡 Hint

Think about the root class that all exceptions inherit from.

System.Exception is the base class for all exceptions in .NET. System.SystemException and System.ApplicationException derive from it. System.Object is the base of all classes but not specifically for exceptions.