C # Bubbling / Event Walkthrough

Question

How to pass event between classes?

I know this sounds ridiculous (and it does), but I have been stumped about this recently. The search did not raise a similar question, so I decided that I would position it.

Here are the objects:

WinForm -> Speaker -> Tweeter
                   -> Woofer

[Speaker, Tweeter, Woofer] all announce the "SpeakToMe" event, which sends a simple string message. Events are declared using a standard template:

public delegate void SpeakToMeHandler(object sender, SpeakToMeEventArgs e);
public event SpeakToMeHandler SpeakToMe;
protected virtual void OnSpeakToMe(string message)
{
   if (SpeakToMe != null) SpeakToMe(this, new SpeakToMeEventArgs(DateTime.Now.ToString() + " - " + message));
}

SpeakToMeEventArgs is a simple class that inherits from EventArgs and contains a Message property.

At their discretion, each of these events works great. For example, I set a button on the form to create, sign, and trigger an event for [Speaker, Tweeter, Woofer]. Each report is returned correctly.

, Speaker [Tweeter, Woofer] .

, [Tweeter, Woofer] , . , :

void tweeter_SpeakToMe(object sender, SpeakToMeEventArgs e)
{
   Console.Out.WriteLine("the tweeter is speaking: " + e.Message);
   this.OnSpeakToMe("tweeter rockin' out [" + e.Message + "]");
}

( ), Console.Out.WriteLine . OnSpeakToMe, , null.

Speaker SpeakToMe . , .

, , ?

Btw, , . [Speaker, Tweeter, Woofer] - . .

, !

: . ! (@David Basarab @Brian) , . , !

Answer 1

, . , , , .

,

OUTPUT

OnSpeak Message = OnSpeakToMeHander Orginal Message: Fired By Tweeter

OnSpeak Message = OnSpeakToMeHander Orginal Message:

class Program
{

    static void Main(string[] args)
    {
        Console.Clear();

        try
        {
            Speaker speaker = new Speaker();
            speaker.speakerEvent += new SpeakToMeHandler(Program.OnSpeak);

            // Cause events to be fied
            speaker.Tweeter.CauseEvent();
            speaker.Woofer.CauseEvent();

        }
        catch (Exception ex)
        {
            Console.WriteLine("Error: {0}", ex.Message);
            Console.WriteLine("Stacktrace: {0}", ex.StackTrace);
        }
    }

    public static void OnSpeak(object sendere, SpeakToMeEventArgs e)
    {
        Console.WriteLine("OnSpeak Message = {0}", e.Message);
    }

}

public delegate void SpeakToMeHandler(object sender, SpeakToMeEventArgs e);

public class SpeakToMeEventArgs : EventArgs
{
    public string Message { get; set; }
}

public class Speaker
{
    public event SpeakToMeHandler speakerEvent;

    public Tweeter Tweeter { get; set; }
    public Woofer Woofer { get; set; }

    public void OnSpeakToMeHander(object sender, SpeakToMeEventArgs e)
    {
        if (this.speakerEvent != null)
        {
            SpeakToMeEventArgs args = new SpeakToMeEventArgs
                {
                    Message = string.Format("OnSpeakToMeHander Orginal Message: {0}", e.Message)
                };

            this.speakerEvent(this, args);
        }
    }

    public Speaker()
    {
        this.Tweeter = new Tweeter();
        this.Woofer = new Woofer();

        Tweeter.tweeterEvent += new SpeakToMeHandler(this.OnSpeakToMeHander);
        Woofer.wooferEvent += new SpeakToMeHandler(this.OnSpeakToMeHander);
    }
}

public class Tweeter
{
    public event SpeakToMeHandler tweeterEvent;

    public void CauseEvent()
    {
        SpeakToMeEventArgs args = new SpeakToMeEventArgs()
            {
                Message = "Fired By Tweeter"
            };

        if (this.tweeterEvent != null)
        {
            this.tweeterEvent(this, args);
        }
    }
}

public class Woofer
{
    public event SpeakToMeHandler wooferEvent;

    public void CauseEvent()
    {
        SpeakToMeEventArgs args = new SpeakToMeEventArgs()
            {
                Message = "Fired By Woofer"
            };

        if (this.wooferEvent != null)
        {
            this.wooferEvent(this, args);
        }
    }
}

Answer 2

if (SpeakToMe != null). (.. ), :

var tmp = SpeakToMe;
if (tmp!=null) tmp(/*arguments*/);

# 6 :

SpeakToMe?.Invoke(e)

MSDN

Answer 3

, null, - , . - ? , .

Answer 4

, .

public class Speaker
{
    public Speaker()
    {
        this.MyTweeter = new Tweeter();
    }

    public Tweeter MyTweeter { get; private set; }

    public event SpeakToMeHandler SpeakToMe
    {
        add { MyTweeter.SpeakToMe += value; }
        remove { MyTweeter.SpeakToMe -= value; }
    }
}

Answer 5

, , ? .

//Handler class
public class Speaker {
    public delegate void HandleMessage(string message);
    public event HandleMessage OnMessage;
    public void SendMessage(string message) {
        if (OnMessage != null) { OnMessage(message); }
    }
}

//then used like...
Speaker handler = new Speaker();
handler.OnMessage += (message) => { Console.WriteLine("Woofer: {0}", message); };
handler.OnMessage += (message) => { Console.WriteLine("Tweeter: {0}", message); };
handler.SendMessage("Test Message");