How to implement (Object sender, EventArgs e) in events?

Hello Guys,

I'm studying events, and i read a lot of articles and tutorials about events, but i can´t understand, how can i declare and use (Object sender, EventArgs e) in my events?

Thanks!

 

So, have your written an event handler yet or are you asking how to do that part? Or, are you asking how to use the passed in parameters in your event handler?

 

My event handler is my delegate method, right? How i can declare the parameters. Can you give me a example in code? I just need see, how i can declare the parameters.

 

For future reference, please provide code snippets. It helps narrow down where you are having problems.

An event is composed of a delegate and an event type. The delegate determines how the event is called and the parameters that are passed. The event type is what the interested parties subscribe to in order to receive the event.

Below is a snippet from Microsoft's event example (here). The parameters are declared in the delegate as you can see in the first couple lines below. You then need to declare the event in the class that will raise it (Changed in the example). Create the method to invoke the event (OnChanged). Finally, signal the event by calling OnChanged where it's needed in the rest of the class such as in Add() in the example below.

Code (CSharp):

1.    // A delegate type for hooking up change notifications.
2.    public delegate void ChangedEventHandler(object sender, EventArgs e);
3.  
4.    // A class that works just like ArrayList, but sends event
5.    // notifications whenever the list changes.
6.    public class ListWithChangedEvent: ArrayList
7.    {
8.       // An event that clients can use to be notified whenever the
9.       // elements of the list change.
10.       public event ChangedEventHandler Changed;
11.  
12.       // Invoke the Changed event; called whenever list changes
13.       protected virtual void OnChanged(EventArgs e)
14.       {
15.          if (Changed != null)
16.             Changed(this, e);
17.       }
18.  
19.       // Override some of the methods that can change the list;
20.       // invoke event after each
21.       public override int Add(object value)
22.       {
23.          int i = base.Add(value);
24.          OnChanged(EventArgs.Empty);
25.          return i;
26.       }
27.  
28.       public override void Clear()
29.       {
30.          base.Clear();
31.          OnChanged(EventArgs.Empty);
32.       }
33.  
34.       public override object this[int index]
35.       {
36.          set
37.          {
38.             base[index] = value;
39.             OnChanged(EventArgs.Empty);
40.          }
41.       }
42.    }
43.