#378 – Implementing an Event

You can subscribe to an event in a class by writing an event handler.  You can also implement events in your own class.

An event is just a class member that is an instance of a delegate type and is declared using the event keyword.

Suppose you’ve defined a delegate type that takes a string parameter:

    public delegate void StringHandlerDelegate(string s);

You can now use this delegate type to define an event in a class.  The event is just an instance of the delegate type.

        public event StringHandlerDelegate Barked;

You can now add code in your class to raise the event. We fire the Barked event from the Bark method.

        public void Bark(string barkSound)
        {
            Console.WriteLine(barkSound);

            // Raise the event
            if (Barked != null)
                Barked(barkSound);
        }

Before invoking the delegate, we make sure it’s not null, to avoid an exception at run-time.