Question

In the most recent version (4.1, released October 2008) of The Microsoft Enterprise Library’s Exception Handling Application Block, there are two HandleException() method signatures, and I am a bit lost on the intent for these, especially since neither the documentation, intellisense, nor the QuickStart apps intimate any meaningful difference.

Here are the two signatures:

bool HandleException(Exception exceptionToHandle, string policyName);

bool HandleException(Exception exceptionToHandle, string policyName, out Exception exceptionToThrow);

All of the examples I have found use the first, as in this example straight out of the XML documentation comments on the actual method:

try
{
   Foo();
}
catch (Exception e)
{
   if (ExceptionPolicy.HandleException(e, name)) throw;
}

And here, from the same source (the XML doc comments for the method), is an example of using the second:

try
{
   Foo();
}
catch (Exception e)
{
   Exception exceptionToThrow;
   if (ExceptionPolicy.HandleException(e, name, out exceptionToThrow))
   {
      if(exceptionToThrow == null)
         throw;
      else
         throw exceptionToThrow;
   }
}

So, my question is, what does using the second one give you that the first does not? This should probably be obvious to me, but my head is a mess today and I don’t really want to keep banging my head against the proverbial wall any longer. 🙂

No speculations, please; I hope to hear from someone that actually knows what they are talking about from experience using this.

Answer 1

If you use a replace handler in the enterprise library config, your replacement exception is returned by means of the second signature .. , out Exception exceptionToThrow).