Events - naming convention and style

Dave Mateer picture Dave Mateer · Apr 7, 2009 · Viewed 65.2k times · Source

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 friend about this tomorrow, and am trying to come up with the most elegant way of explaining the concepts. (thought the best way to understand a subject is to try and teach it!)

class Program
    {
        static void Main()
        {
            // setup the metronome and make sure the EventHandler delegate is ready
            Metronome metronome = new Metronome();

            // wires up the metronome_Tick method to the EventHandler delegate
            Listener listener = new Listener(metronome);
            metronome.OnTick();
        }
    }

public class Metronome
    {
        // a delegate
        // so every time Tick is called, the runtime calls another method
        // in this case Listener.metronome_Tick
        public event EventHandler Tick;

        public void OnTick()
        {
            while (true)
            {
                Thread.Sleep(2000);
                // because using EventHandler delegate, need to include the sending object and eventargs 
                // although we are not using them
                Tick(this, EventArgs.Empty);
            }
        }
    }

public class Listener
    {
        public Listener(Metronome metronome)
        {
            metronome.Tick += new EventHandler(metronome_Tick);
        }

        private void metronome_Tick(object sender, EventArgs e)
        {
            Console.WriteLine("Heard it");
        }
    }

n.b. Code is refactored from http://www.codeproject.com/KB/cs/simplesteventexample.aspx

Answer

YotaXP picture YotaXP · Apr 7, 2009

Microsoft has actually written extensive set of naming guidelines and put it in the MSDN library. You can find the articles here: Naming Guidelines

Aside from the general capitalization guidelines, here is what it has for 'Events' on the page Names of Type Members:

✔️ DO name events with a verb or a verb phrase.

Examples include Clicked, Painting, DroppedDown, and so on.

✔️ DO give events names with a concept of before and after, using the present and past tenses.

For example, a close event that is raised before a window is closed would be called Closing, and one that is raised after the window is closed would be called Closed.

❌ DO NOT use "Before" or "After" prefixes or postfixes to indicate pre- and post-events. Use present and past tenses as just described.

✔️ DO name event handlers (delegates used as types of events) with the "EventHandler" suffix, as shown in the following example:

public delegate void ClickedEventHandler(object sender, ClickedEventArgs e);

✔️ DO use two parameters named sender and e in event handlers.

The sender parameter represents the object that raised the event. The sender parameter is typically of type object, even if it is possible to employ a more specific type.

✔️ DO name event argument classes with the "EventArgs" suffix.