What's the standard to make an event that doesn't pass any information along?

I've got an event that literally just lets the user know something happened. They have to manually take action for that event, as no data is passed from it.

However, I'm not sure what would be more idiomatic:

public event Action MyEvent;
//clearly says no arguments
public event EventHandler MyEvent;
//uses the EventHandler class to no effect, but might be more idiomatic.
public event Action<object> MyEvent;
//just like the first but passes the sender if needed.

Which would be the standard way to do this?

Jon Skeet
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The idiomatic approach would be to just use EventHandler. Pass in an appropriate sender if you have one or null otherwise, and EventArgs.Empty.

I know it's somewhat crazy, but that's the convention. Bear in mind that plain EventArgs has no useful information in it, so any EventHandler-based event is basically saying "I may get a sender, but that's probably all."

However, with delegate variance as of C# 2, there is a benefit to this: you can use the same event handling method for all events which follow the convention... so you can have (say) logging event handlers which use reflection to dump whatever information they are given in the EventArgs, even if they don't know about it at compile-time.

It's not the greatest argument in the world for a convention, admittedly - but it's a reasonably strong one. Of course routed events are slightly different in how they're subscribed, but even so the delegates follow the same pattern.

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