Question

I have some code in my project that saves an object to the database, once this is done I want it to call a series of other methods.

I was thinking about allowing other methods to subscribe to this event so I can add more as I need to. The idea I had for this was to create an array of Delegates allowing other methods to register, then when the object had been saved it could loop through the delegates and call each one.

Would this be bad practise or is there a better way of doing this?

Thanks

Answer 1

You can subscribe as many delegates as you want to a single event. Under the hood .Net keeps these as an ordered collection anyway.

The standard pattern for this is:

//in your class
public EventHandler<MyEvtArgs> MyEvent;

protected void OnMyEvent ( MyEvtArgs args ) {
    if(MyEvent != null) //make sure there is at least 1 subscriber
        MyEvent(this, args);
}

Then to call this:

var myInstance = new MyClass();

// all of these can convert to EventHandler<MyEvtArgs> (object, MyEvtArgs)
myInstance.MyEvent += (sender, e) => { /* do something 1 */ };

myInstance.MyEvent += (sender, e) => { /* do something 2 */ };

myInstance.MyEvent += localMethod;

Now when your protected OnMyEvent method is called inside your class all of these events will fire – in order.

You can also remove items from this collection:

myInstance.MyEvent -= localMethod;