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C# › Exception Handling

Why does 'throw;' (bare throw) preserve the original stack trace, while 'throw ex;' does not?

Intermediate

Answer

'throw;' re-throws the CURRENT exception exactly as caught, preserving its original stack trace all the way back to where it was FIRST thrown; 'throw ex;' treats it as throwing a NEW exception from THIS point, overwriting the stack trace and losing the original throw location — making the bare 'throw;' the correct choice when re-throwing after logging or partial handling.
try {
  DoSomethingRisky();
} catch (Exception ex) {
  LogError(ex);
  throw;     // CORRECT: preserves the original stack trace
  // throw ex; // WRONG: resets the stack trace to this line
}
Real-world example Logging an exception's details before re-throwing it, without losing the diagnostic value of the original stack trace.

Common follow-ups: Is there any legitimate reason you'd deliberately want to use 'throw ex;' instead of bare 'throw;'?

Fundamentals
All 16 Exception Handling questions