Should I use EventArgs or a simple data type?

Question

I'm currently creating a library for fun and practice and I was wondering, when raising an event, how to choose between passing your own EventArgs derivative or just the data type.

For example, in my library I have something like this:

public delegate void LostConnectionEventHandler(string address);
public delegate void MessageReceieved(byte[] bytes);

What is the standard practice for this? Should I replace string address with ConnectionEventArgs and byte[] bytes with MessageEventArgs?

I know either one works just fine and this question may be subjective but I am still curious on the thought process higher-level programmers go through when deciding whether or not to include their own EventArgs or just to pass the data in directly.

Thanks!

Answer 1

The .NET Framework guidelines indicate that the delegate type used for an event should take two parameters, an "object source" parameter indicating the source of the event, and an "e" parameter that encapsulates any additional information about the event. The type of the "e" parameter should derive from the EventArgs class. For events that do not use any additional information, the .NET Framework has already defined an appropriate delegate type: EventHandler.

Reference: http://msdn.microsoft.com/en-us/library/aa645739(v=vs.71).aspx

Another useful information: http://msdn.microsoft.com/en-us/library/ms229011.aspx