Raising events vs direct method calls differences

Question

Raising an event, will call its event handler. eg http://msdn.microsoft.com/en-us/library/aa645739%28VS.71%29.aspx

What is the difference between using the events mechan

Answer 1

What is the difference between using the events mechanism and direct calls to other methods (eg if a condition is met in method A(), call B() )?

Business logic wise there is no difference between the two. What I mean by this is that you can accomplish the same task each way. It's just a different way of going about it. The real difference is the amount of work you have to do to handle the notification of other modules.

With raising an event, you are essentially saying "Hey, something has occurred any piece of code which has signed up to be notified when this happened, let them know. Which modules that get notified is not my concern, because I am assuming that (at runtime) all modules that need to know are setup for notification."

With calling each method directly, you are making the decision that you are going to tell this (or these) modules, and only these, that something has occurred. You are making that assertion that no matter what the states of these modules are in isn't important and they need to know this event happened.

Both are correct for different situations. Event notifications are more dynamic. Different modules can register and de-register for notifications. Direct method calls are more static. A certain set of objects (or modules etc.) are absolutely going to be notified (barring exceptions of course) that something happened, but only these are going to be notified.