How to dispatch events in C#

Question

I wish to create own events and dispatch them. I never done this before in C#, only in Flex.. I guess there must be a lot of differencies.

Can anyone provide me a good example?

Answer 1

Look into 'delegates'.

• Define a delegate
• Use the delegate type as field/property (adding the 'Event' keyword)
• You are now exposing events that users can hook into with "+= MyEventMethod;"

Hope this helps,

Answer 2

Events in C# use delegates.

public static event EventHandler<EventArgs> myEvent;

static void Main()
{
   //add method to be called
   myEvent += Handler;

   //call all methods that have been added to the event
   myEvent(this, EventArgs.Empty);
}

static void Handler(object sender, EventArgs args)
{
  Console.WriteLine("Event Handled!");
}

Answer 3

There is a pattern. Here is an example based on the simplest event-delegate,

// the delegate type, from the library, in the System namespace
public void Eventhandler(object sender, Eventargs args);  

// your class
class Foo  
{
    public event EventHandler Changed;  // the event

    protected virtual void OnChanged()
    {
        EventHandler handler = Changed; // make a copy to be more thread-safe
        if (handler != null)
        {
            handler(this, EventArgs.Empty);
        }
    }
}

And how to use it:

class Bar
{
    void OnFooChanged(obkect sender, EventArgs args)  // handle (react)
    {
        //
    }

    void Setup()
    {
        Foo f = ....

        f.Changed += OnFooChanged;  // subscribe
    }
}

Answer 4

Using the typical .NET event pattern, and assuming you don't need any special arguments in your event. Your typical event and dispatch pattern looks like this.

public class MyClassWithEvents
    {
        public event EventHandler MyEvent;

        protected void OnMyEvent(object sender, EventArgs eventArgs)
        {
            if (MyEvent != null)
            {
                MyEvent(sender, eventArgs);
            }
        }

        public void TriggerMyEvent()
        {
            OnMyEvent(sender, eventArgs);
        }
    }

Tying something into the event can be as simple as:

public class Program
{
    public static void Main(string[] args)
    {
        MyClassWithEvents obj = new MyClassWithEvents();

        obj.MyEvent += obj_myEvent;
    }

    private static void obj_myEvent(object sender, EventArgs e)
    {
        //Code called when my event is dispatched.
    }
}

Take a look at the links on this MSDN page