VS 2005 - C# Event

You can remove existing event handler before adding new one:

button1.Click -= new EventHandler(this.button1_Click);
button1.Click += new EventHandler(this.button1_Click);

This doesn't fail also if currently there is no association.

if (button1.Click ==null)
button1.Click += new EventHandler(this.button1_Click);

Hi Desp,
Received following error message:

The event 'System.Windows.Forms.Control.Click' can only appear on the left hand side of += or -=C:\WindowsApplication2\Source.cs      32      25      MyApp

Create a method as follows:

        public void AddEventHandler(EventHandler handler)
        {
            if (Event != null)
            {
                bool addHandler = true;
                Delegate[] d = Event.GetInvocationList();

                foreach (Delegate de in d)
                {
                    if (handler.Target == de.Target)
                    {
                        addHandler = false;
                        break;
                    }
                }
                if (addHandler)
                {
                    Event += handler;
                }
            }
            else
            {
               Event += handler;
            }
        }

That way you will ensure that the handler will only get added if it hasnt been added already.

Hope that helps.

Hi Seraph_78,

Where is Event declared and declared as what type?

If its button1.Click event then I probably will have the same error
message mentioned in the previous comment.

Thanks.

Event is just name for an event.  So yes button1.Click.
The code ensures that you dont attach the same handler more than once.

If you are getting the error mentioned before are you sure you are attaching the handler to the event and not somehow having the event on the right hand side of the asignment.

Hi,

The compiler error message occurred at the statement when I test if the event is null.
It occurred before any assignment of handler.
It says the "event" can only appear on the left of  either += or -=.

Am I missing something here or I have misunderstood some important point?
Please help. Thanks.