C# delegate v.s. EventHandler

Question

I want to send an alert message to any subscribers when a trap occurred.

The code I created works fine using a delegate method myDelegate del.

My qu

Answer 1

The difference between event and delegate is that:

event declaration adds a layer of protection on the delegate instance. This protection prevents clients of the delegate from resetting the delegate and its invocation list, and only allows adding or removing targets from the invocation list

See What are the differences between delegates and events?

2) As I see it, your subscriber should not change delegates freely. One subscriber can assign = to it instead of adding +=. This will assign a new delegate, therefore, the previous delegate with its invocation list will be lost and previous subscribers will not be called anymore. So you should use Event for sure. Or you can change your code to make your delegate private and write additional functions for manipulating it to define your own event behavior.

 //preventing direct assignment
 private myDelegate del ;

    public void AddCallback(myDelegate m){
        del += m;
    }

    public void RemoveCallback(myDelegate m){
        del -= m;
    }

    //or
    public static trap operator +(trap x,myDelegate m){
        x.AddCallback(m);
        return x;
    }
    public static trap operator -(trap x, myDelegate m)
    {
        x.RemoveCallback(m);
        return x;
    }

//usage  

//t.AddCallback(new trap.myDelegate(notify));
  t+=new trap.myDelegate(notify);