Events - naming convention and style

Question

I\'m learning about Events / Delegates in C#. Could I ask your opinion on the naming/coding style I\'ve chosen (taken from the Head First C# book)?

Am teaching a fr

Answer 1

There are a few points that I would mention:

Metronome.OnTick doesn't seem to be named correctly. Semantically, "OnTick" tells me it will be called when it "Tick"s, but that isn't really what's happening. I would call it "Go" instead.

The typically accepted model, however would be to do the following. OnTick is a virtual method that raises the event. This way, you can override the default behavior in inherited classes easily, and call the base to raise the event.

class Metronome
{
    public event EventHandler Tick;

    protected virtual void OnTick(EventArgs e)
    {
        //Raise the Tick event (see below for an explanation of this)
        var tickEvent = Tick;
        if(tickEvent != null)
            tickEvent(this, e);
    }

    public void Go()
    {
        while(true)
        {
            Thread.Sleep(2000);
            OnTick(EventArgs.Empty); //Raises the Tick event
        }
    }
}

---

Also, I know this is a simple example, but if there are no listeners attached, your code will throw on Tick(this, EventArgs.Empty). You should at least include a null guard to check for listeners:

if(Tick != null)
    Tick(this, EventArgs.Empty);

However, this is still vulnerable in a multithreaded environment if the listener is unregistered between the guard and the invocation. The best would be to capture the current listeners first and call them:

var tickEvent = Tick;
if(tickEvent != null)
    tickEvent(this, EventArgs.Empty);

I know this is an old answer, but since it's still gathering upvotes, here's the C# 6 way of doing things. The whole "guard" concept can be replaced with a conditional method call and the compiler does indeed do the Right Thing(TM) in regards to capturing the listeners:

Tick?.Invoke(this, EventArgs.Empty);