Raise Base Class Events in Derived Classes C#

Question

I have a base class DockedToolWindow : Form, and many classes that derive from DockedToolWindow. I have a container class that holds and assigns events to DockedToolWindow objects, however I want to invoke the events from the child class.

I actually have a question about how to implement what this MSDN site is telling me to do. This section below is giving me the problem:

    // The event. Note that by using the generic EventHandler<T> event type
    // we do not need to declare a separate delegate type.
    public event EventHandler<ShapeEventArgs> ShapeChanged;

    public abstract void Draw();

    //The event-invoking method that derived classes can override.
    protected virtual void OnShapeChanged(ShapeEventArgs e)
    {
        // Make a temporary copy of the event to avoid possibility of
        // a race condition if the last subscriber unsubscribes
        // immediately after the null check and before the event is raised.
        EventHandler<ShapeEventArgs> handler = ShapeChanged;
        if (handler != null)
        {
            handler(this, e);
        }
    }

Sure this example compiles and works, but when I replace "ShapeChanged" with "Move" (an event I acquired from deriving from Form), it errors saying I cannot have Move on the right side without += or -=. I also removed the ShapeEventArgs generic tags.

Any incite on why this isn't working? What's the difference between an event declared within the class and one that is inherited?

Answer 1

You cannot directly fire base class events. This is exactly the reason why you had to make your OnShapeChanged method protected instead of private.

Use base.OnMove() instead.