Inform client application or arrange internal state first?

Question

Let's say we have a client application that uses a network stack. The stack detects an error condition that leads the stack to close it's connection and raises a ConnectionStateChanged event. Besides that the stack raises an ErrorOccured event to inform the client appplication about the error condition.

So what to do first? Arrange the internal state (and raise the ConnectionStateChanged event) or inform the client application (raise the ErrorOccured event)?

[EDIT]This question is not about the user interface or any user interaction. It is only about the behaviour of the network stack (or any other underlying component).[/EDIT]

Answer 1

I try to abide by these three rules:

1. Never allow a user to work with an application in an inconsistent state. This allows at the very least to unexpected behavior and probably to subtle (and not so subtle) bugs.
2. Always try to handle errors automatically, without informing the user. The less cognitive hassle for the user, the more usable your app is. Of course there are errors that have to be notified to the user.
3. Always try to inform the user as soon as possible of any relevant error that wasn't handled automatically. After the two above rules, inform as soon as possible so the user isn't kept wondering about what is happening, provide visual feedback constantly, if appropriate.

So, I'd have the application to fix its internal state, then inform the user, but only if it's really necessary (maybe implement a retry scheme, for example.)

EDIT: In the case where user means actually a client application, I think that rule 1 still applies. If you return to the client application before having your internal state consistent, the client application could send immediately a new request when your state is still inconsistent. So you could, either choose to do a check on every request to see if you are in an inconsistent state and raise a NotReady event, or just avoid that check and only return control to the client only when you are ready.