Thread: Events

I am a little confuzed with events.
To use them first you define a delegate signature. Like:

Code:

public delegate void ButtonEventHandler();

Then we make a delegate (event) in our class. Like:

Code:

class TestButton 
{
    public event ButtonEventHandler OnClick;

    // A method that triggers the event:
    public void Click()
    {
        OnClick();
    }
}

The class has a method or methods that trigger the event. The event is just a delegate that Click() invokes.

For handling events we subscribe handlers to events. That is exactly adding more methods to a delegate (Except when accessors are used). Like:

Code:

 TestButton mb = new TestButton();
        
 // Specify the method that will be triggered by the OnClick event.
 mb.OnClick += new ButtonEventHandler(TestHandler);

 // Specify an additional anonymous method.
 mb.OnClick += delegate { System.Console.WriteLine("Hello, World!"); };

And event will be triggered by calling Click() method. Like:

Code:

 // Trigger the event
 mb.Click();

Everything is going fine. By raising the event, Click() method invokes OnClick event and because it is like a delegate it calls subscribed methods that are actually event handlers.
Now my question is: What is the difference between a delegate and an event? A delegate has the same functionality of an event. What will happen if we don't write event keyword in the class?

I have also another question: Why MSDN writes this:

Code:

m_list.Changed += new ChangedEventHandler(ListChanged);

When it can be written as this:

Code:

m_list.Changed += ListChanged;

???