events & delegates

[PT Exorcist]

hmmm i've been reading about this and i got a few questions about it...

hmm...what is the advantage of my class inherit from EventArgs? if i do so i can't make my class inherit from anymore class so it looks like a disavantage

and...i want to have events that has different parameters between them...do i have to have 1delegate for each "type" of parameters? maybe the answer is inheriting from EventArgs..omg..i am not getting this lol

[Scott Penner]

It depends what you are trying to do...

If you are trying to supply an event procedure, like from a user control, for any custom event you want, you will need to create a class inherited from EventArgs. Actually, the way I understand this from MS is that if you want others to be consuming these events like for a class library or user control, then you should pack any custom arguments into a EventArgs subclass.

Are delegates CLS-Compliant? I'm not sure VB has delegates...

If however you are looking for something more like a C callback function, something that you are using internally, you should use just a delegate. The delegate object will be a bit more direct than stuffing all the arguments into your EventArgs subclass.

hmmm....after reading your post again, I'm not sure I answered your question...

Only arguments for custom event procedures need to be a subclass of EventArgs. If you have some simple events, like a simple notification, you can just use the standard EventArgs class.

// simple notification:
public delegate void ChangedEventHandler(object sender, EventArgs e); 

If you want to add some other parameters to the event, then create a class, CustomEventArgs inherited from EventArgs that have some additional public properties.

// custom notification:
public delegate void CustomEvent(object sender, CustomEventArgs e); 

...let me know if that's still confusing and I will try again...

[DevGrp]

Yes VB has delegates.

[PT Exorcist]

i want to make a class that has events...but how do i make that several events use the same delegate if they have different parameters?

[DevGrp]

You cant. The method you are calling have to have the same signiture of the delegate, so each event that you want to have a diferent parameter, must match the delegate that will invoke it.

eg:

public delegate int CompareNumsDelegate(int num1, int num2);

//method
int MyFunc(int num1, int num2)
{
      if(num1 > num2)
      {
           return num1;
      }
      else
           return 0;
}

CompareNumsDelegate comDel = new CompareNumsDelegate(MyFunc);

You can now call comDel just as if it was the function MyFunc like this:

comDel(5,2);

[PT Exorcist]

so thats why ppl put things under EventArgs?

if yes how do i do that?

[DevGrp]

so thats why ppl put things under EventArgs?

What do you mean?

[PT Exorcist]

i have a class for internet i want an event for Connected other for Disconnected blablabla they all have different parameters...will i have to make 300 delegates + 300 events? omg there must be another way

[DevGrp]

I'm sure you wont need all 300 . What I would do is make classes inheriting from EventArgs, then extending those classed to include the functionality for events that you would like.

eg.
Class DisconnectedEventHandler
Class ConnectedEventHandler

Then group the functionality.

[PT Exorcist]

im not getting

[DevGrp]

What are the events that you need?

[PT Exorcist]

lets imagine i want this events:

connected(string ip)
disconnected(string exitMessage, string ip)

receivedMessage(string message, string ip, string nickName)
etc..

will i have to make a delegate for each one of these because they all have differente params?

[DevGrp]

Yes.

[PT Exorcist]

oh great..lol

[PT Exorcist]

ah what names do u give to the delegates?
maybe givin them names like param1 meaning this has only 1 param would help or no? lol to me this thing of delegates is the worse **** ever...in vb.net we have delegates but dont have to use them in events what seems a LOT better

[PT Exorcist]

hmm the usual when programming in C# is somewhat for each event a delegate?

[PT Exorcist]

how do i make to put delegates and events in the same class?

the book only says how to put the delegates under the same namespace...

upper:

namespace WindowsApplication5
{
        public delegate void Event(string message); 

class

    class TESTE
    {
        public event Event teste;

        private void lol()
        {
            teste("...");
        }

        
    } 

form

        private void Form1_Load(object sender, System.EventArgs e)
        {
            TESTE test = new TESTE();
            test.teste += new Event(my_teste);
            my_teste("lol...");
        }

        private void my_teste(string mensagem)
        {
            MessageBox.Show(mensagem + "\nlol sukas");
        }

    } 

[DevGrp]

Ok, I have a little example;

//Class with your events and delegates
public class Tester
{
    public delegate void ConnectedHandler(string ip);
    public delegate void DisconnectedHandler(string exitMsg, string ip);
    public delegate void ReceivedMessageHandler(string msg, string ip, string nick);
        
    public event ConnectedHandler Connected;
    public event DisconnectedHandler Disconnected;
    public event ReceivedMessageHandler ReceiveMessage;
        
    public Tester()
    {
    }

    public void Connect(string ip)
    {
        if(Connected != null)
        {
            Connected("Connected to " + ip);
        }
    }
    public void Disconnect(string ip)
    {
        if(Disconnected != null)
        {
            Disconnected("Disconnected from ", "191.168.0.1");
        }
    }
    public void Receive()
    {
        if(ReceiveMessage != null)
        {
            ReceiveMessage("How are you", "191.168.0.1", "Dev");
        }
    }
} 

Using the Events

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

namespace TestEvents
{
    
    public class Form1 : System.Windows.Forms.Form 
    {
        private System.Windows.Forms.Button button1;
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.Container components = null;
        private System.Windows.Forms.FolderBrowserDialog fd;
        private System.Windows.Forms.Button button2;
        private System.Windows.Forms.Label label1;
        Tester t = new Tester();
                
        public Form1()
        {
            //
            // Required for Windows Form Designer support
            //
            InitializeComponent();
            
            //
            // TODO: Add any constructor code after InitializeComponent call
            //
            Application.EnableVisualStyles();
            
            t.ReceiveMessage +=new TestEvents.Tester.ReceivedMessageHandler(t_ReceiveMessage);
            t.Connected +=new TestEvents.Tester.ConnectedHandler(t_Connected);   
            t.Disconnected +=new TestEvents.Tester.DisconnectedHandler(t_Disconnected);
                        
        }
        private void Form1_Load(object sender, System.EventArgs e)
        {
            t.Connect("191.168.0.1");
            t.Disconnect("191.168.0.1");
            t.Receive();
        }
        private void t_Connected(string ip)
        {
            MessageBox.Show(ip);
        }

        private void t_Disconnected(string exitMsg, string ip)
        {
            MessageBox.Show(exitMsg + ip);
        }

        private void t_ReceiveMessage(string msg, string ip, string nick)
        {
            MessageBox.Show(msg + " " + nick + " from " + ip);
        }
    }
} 

[PT Exorcist]

ah ill have to put this always in the form?

t.ReceiveMessage +=new TestEvents.Tester.ReceivedMessageHandler(t_ReceiveMessage);
t.Connected +=new TestEvents.Tester.ConnectedHandler(t_Connected);
t.Disconnected +=new TestEvents.Tester.DisconnectedHandler(t_Disconnected);

bleh..thats g@y

[PT Exorcist]

imagine i have a class that i do..then i send that class to my friend..in order to put that class + class' events working he'll have to put that

t.ReceiveMessage +=new TestEvents.Tester.ReceivedMessageHandler(t_ReceiveMessage);
t.Connected +=new TestEvents.Tester.ConnectedHandler(t_Connected);
t.Disconnected +=new TestEvents.Tester.DisconnectedHandler(t_Disconnected);

things in his form? isnt there an hit and run like vb way of doin this? it seems so complicated damn...waste of time in comp. with vb

[hellswraith]

It seems like a waste of time, but the advantages outweight the inconvienence. You can add more than one procedure to be called to the delegate if you want. This means that if you have multiple forms that must recieve the event, they can all subscribe to the event. Another way they are useful is you can turn off and on the event at run time.

Now, if you create a control with events, the user of your control should be able to let the IDE subscribe to the event for them by clicking the Event button in the properties window and double clicking the event.

What they provide is more flexibility.

Sure VB hides it from you, but can you really call yourself a programmer without knowing how they really work?...lol.

[PT Exorcist]

it just seems damn confusing

[PT Exorcist]

ah i think im getting in now after watching carefully DevGroup's example..but it's still confusing lolol

[PT Exorcist]

woohooo tested in a class now made by me and worked lol i rule

[DevGrp]

Good to know that it works and you're finally getting it. Dont worry about the confusion, it will pass . Sometimes it still a little confusing for me, then I have to pull out my notes .

[PT Exorcist]

now i saw a class i downloaded from net and only now i realised that for each event i have to make a delegate..i though there was a way to have only 1delegate for all events lol