All 16 Exception Handling questions
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What is the purpose of the finally block? How does a try/catch block work in C#, and what happens if no matching catch clause exists? What does the finally block guarantee, and when is it commonly used? When should you use using or await using? What are exception filters (when) and why use them? How do custom exception classes work in C#, and what's the recommended convention for creating one? What is exception filtering using the 'when' clause, and what advantage does it offer over catching and manually re-throwing? Why does 'throw;' (bare throw) preserve the original stack trace, while 'throw ex;' does not? When should you create custom exceptions vs use built-in ones? What is the recommended strategy for exceptions in a layered/enterprise app?
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C# › Exception Handling

What is the difference between throw and throw ex inside a catch?

Beginner

Answer

throw re-throws preserving the original stack trace; throw ex resets the stack trace to the current line, losing where the error really happened.
catch (Exception ex) { Log(ex); throw; }      // good
catch (Exception ex) { throw ex; }             // loses stack trace
Real-world example Preserving the original stack trace is essential for diagnosing production errors.
All 16 Exception Handling questions