Question

I have a class ‘b’ that inherits from class ‘a’. In class ‘a’ there is some code that performs an action if an event is not null. I need that code to fire in class ‘b’ during specific times in the application. So in ‘b’ I subscribed to a new Handler(event).

If I leave the autogenerated event ‘as is’ in class ‘b’ with the throw new NotImplementedException(); line, the code works/runs as expected. As soon as I remove the thow exception, the application no longer works as expected.

So, what is the throw new NotImplementedException doing besides throwing the exception?

I realize I’m probably trying to solve my coding problem the wrong way at this point, and I am sure I will find a better way to do it (I’m still learning), but my question remains. Why does that line change the outcome of code?

EDIT:
I reallize I wan’t very specific with my code. Unfortunately, because of strict policies, I can’t be. I have in class ‘a’ an if statement.

if (someEvent != null)

When the code ‘works’, the if statement is returning true. When it isn’t working as expected, it is returning ‘false’. In class ‘b’, the only time the application ‘works’ (or the if statement returns true), is when I have the throw new NotImplementedException(); line in class ‘b’s event method that is autogenerated when I attached the new event.

Answer 1

It is simply an exception, as for why it means your application “works” is entirely dependent on the code handling any exceptions.

It is not a “special” exception as opposed to a normal exception (other than being derived from Exception like the rest). You tend to see it with code generation as a placeholder for implementing the member it is throwing inside. It is a lot easier to do this than have code generation try to understand the member structure in order to output compiling code.

When you say “no longer works as expected”, I am assuming it compiles. If removing this stops the code from compiling then the chances are good you have a compilation error about a return value.

Perhaps the code that triggers the event expects a certain response from handlers, or if there are no handlers or exceptions occur it defaults the response and carries on. In your case, there is a handler and no exception so it expects a better response?

Complete guesswork.

If there is code in a that you need to use in b, consider making the method that houses the code protected and optionally virtual if you need to override the behaviour.