Why is TargetInvocationException treated as uncaught by the IDE?

Question

I have some code that is using reflection to pull property values from an object. In some cases the properties may throw exceptions, because they have null references etc.

                    object result;
                    try
                    {
                        result = propertyInfo.GetValue(target, null);

                    }
                    catch (TargetInvocationException ex)
                    {
                        result = ex.InnerException.Message;
                    }
                    catch (Exception ex)
                    {
                        result = ex.Message;
                    }

Ultimately the code works correctly, however when I am running under the debugger : When the property throws an exception, the IDE drops into the debugger as if the exception was uncaught. If I just hit run, the program flows through and the exception comes out as a TargetInvocationException with the real exception in the InnerException property.

How can I stop this from happening?

Answer 1

EDIT: I've just tried this myself, and it looks like reflection is treated slightly differently. You might want to think of a reflection call as starting a new level of "handled" as far as the debugger is concerned: nothing is catching that exception before it gets translated and rethrown as a TargetInvocationException, so it breaks in. I don't know if there's any way of inhibiting that - but does it happen very often? If you're regularly performing lots of operations which result in exceptions, you might want to reconsider your design.

---

Original answer

Go to Debug / Exceptions... and see what the settings are. You'll see this behaviour if TargetInvocationException (or anything higher in the hierarchy) has the "Thrown" tickbox checked.

Answer 2

Hm, it appears to be a bug in Visual Studio. Thanks for letting us know, we're looking at it.

EDIT: I've followed up and this seems to be "by design". What happens is that you likely have Tools -> Options -> Debugging -> General -> Enable Just My Code.

As the help file here states: http://msdn.microsoft.com/en-us/library/038tzxdw.aspx The Debug -> Exceptions dialog shows an additional column (Break when an exception is User-unhandled) when "Enable Just My Code" is on. Essentially this means that whenever the exception is leaving the boundary of your code (and in this case, it falls through down to the .NET framework reflection code), VS breaks because it thinks that the exception has left the user code. It doesn't know that it will return into the user code later in the stack.

So there are two workarounds: Disable Just My Code in Tools -> Options -> Debugging -> General or Remove the check box from the User-unhandled .NET Framework exceptions in the Debug -> Exceptions dialog.

Hope this helps!