#381 – Implementing an Event that Returns Some Data

When you implement an event, you can define your own delegate type, or you can use the existing EventHandler or EventHandler<TEventArgs> types.

If you want your event to return some data, you should:

  • Create a new class that inherits from EventArgs for the event’s data
  • Use the EventHandler<TEventArgs> delegate type

Start by defining new EventArgs-based class that will store the event’s data.

    public class BarkedEventArgs : EventArgs
    {
        public string BarkSound { get; protected set; }
        public BarkedEventArgs(string barkSound)
        {
            BarkSound = barkSound;
        }
    }

Then, in your class, declare the event and a helper method to raise the event.

        // Declare the event
        public event EventHandler<BarkedEventArgs> Barked;

        // Helper method that raises the event
        protected virtual void OnBarked(string sound)
        {
            if (Barked != null)
                Barked(this, new BarkedEventArgs(sound));
        }

Finally, raise the event whenever a Dog barks.

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

            OnBarked(barkSound);
        }
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About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

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