What does “throw new NotImplementedException();” do exactly?

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\'

Answer 1

Think about this: what if you want to add two integers with the following method...

private int Add(int x, int y)
{

}

...and have no code inside to do such (the method doesn't even return an integer). This is what NotImplementedException is used for.