The difference between re

Suppose I have the following two classes in two different assemblies:

//in assembly A
public class TypeA {
   // Constructor omitted
   public void MethodA
   {
     try {
       //do something
     }
     catch {
        throw;
     }
   }
}
//in assembly B
public class TypeB {
   public void MethodB
   {
     try {
       TypeA a = new TypeA();
       a.MethodA();
     }
     catch (Exception e)
       //Handle exception
     }
   }
}

In this case, the try-catch in MethodA just elevates the exception but doesn't really handle it. Is there any advantage in using try-catch at all in MethodA? In other words, is there a difference between this kind of try-catch block and not using one at all?

---

In your example, there is no advantage to this. But there are cases where it is desirable to just bubble up a specific exception.

    public void Foo()
    {
        try
        {
            // Some service adapter code

            // A call to the service
        }
        catch (ServiceBoundaryException)
        {
            throw;
        }
        catch (Exception ex)
        {
            throw new AdapterBoundaryException("some message", ex);
        }
    }

This allows you to easily identify which boundary an exception occurred in. In this case, you would need to ensure your boundary exceptions are only thrown for code specific to the boundary.

---

Yes there is a difference. When you catch an exception, .NET assumes you are going to handle it in some way, the stack is unwound up to the function that is doing the catch.

If you don't catch it will end up as an unhandled exception, which will invoke some kind of diagnostic (like a debugger or a exception logger), the full stack and its state at the actual point of failure will be available for inspection.

So if you catch then re-throw an exception that isn't handled elsewhere you rob the diagnostic tool of the really useful info about what actually happened.

---

Taken as-is, the first option would seem like a bad (or should that be 'useless'?) idea. However, it is rarely done this way. Exceptions are re-thrown from within a Catch block usually under two conditions :

a. You want to check the exception generated for data and conditionally bubble it up the stack.

try 
{
  //do something
}
catch (Exception ex)
{
  //Check ex for certain conditions.
  if (ex.Message = "Something bad")
    throw ex;
  else
    //Handle the exception here itself.
}

b. An unacceptable condition has occurred within a component and this information needs to be communicated to the calling code (usually by appending some other useful information or wrapping it in another exception type altogether).

try 
{
  //do something
}
catch (StackOverflowException ex)
{
    //Bubble up the exception to calling code 
    //by wrapping it up in a custom exception.
    throw new MyEuphemisticException(ex, "Something not-so-good just happened!");
}

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