Question

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What is the proper way to re-throw an exception in C#?

I want to understand why the “throw ex” usage hides the original stack trace? What was the fundamental philosophy behind the scene when designing c# compiler?

Answer 1

This isn’t actually a C# question, but rather a CLI design question, and comes down to the different IL instructions, throw and rethrow.

Basically, throw ex; (for any ex, even the original) is an IL throw, where-as throw; is an IL rethrow.

If you are specifying a specific exception to throw, it follows that this exception is logically originating from here, now, this method. If that isn’t the case, then either:

throw;

rather than throw ex;, or: wrap the exception in another exception, so you preserve the original exception and show where the new one came from:

throw new SomeException(ex);

in which case the caller can obtain the original stack trace via ex.InnerException.