Exception handling

C# uses exceptions for exceptional error paths—similar to Java but without checked exceptions. Combine try/catch/finally with using for deterministic resource cleanup via IDisposable.

try / catch / finally

try {
    throw new InvalidOperationException("failed");
} catch (InvalidOperationException ex) {
    Console.WriteLine(ex.Message);
} finally {
    Console.WriteLine("cleanup");
}

Custom exceptions

class AppException : Exception {
    public AppException(string message) : base(message) { }
}

Throw specific types; catch the most specific exception first. Use exceptions for unexpected failures—not routine control flow.

Important interview questions and answers

1. Q: Exceptions vs Result types?
   A: Exceptions unwind the stack for rare failures; Result/either patterns suit expected errors in functional-style APIs.
2. Q: finally vs using?
   A: using calls Dispose deterministically; finally runs on all exit paths including exceptions.

Self-check

1. What runs in finally when an exception is thrown?
2. Base type for catching all managed exceptions?

Tip: Catch specific exceptions first—avoid empty catch blocks that swallow errors and hide bugs in production.