Can I cast event args inside the called function in C# instead of defining delegates?

I have an event:

public event RoutedEventHandler ActionEvent;

I have a superclass:

internal class MyEventArgs : RoutedEventArgs
{
    public enum SomeAction
    {
        ACTION1,
        ACTION2,
        ACTION3
    }

    public MyEvent(SomeAction action)
    {
        this.action = action;
    }

    public SomeAction action;
}

I call the function:

private void onAction(object sender, MyEventArgs args) { if (ActionEvent != null) ActionEvent(sender, args); }

And finally, hence my question, I cast inside the called method:

void ActionEvent(object sender, RoutedEventArgs e)
{
    MyEvent args = (MyEvent)e;
}

Is this legal? Can I avoid introducing delegates? It compiles and runs happily in debug mode.

(I'm new in C#. I have been using C++ for ages. The answer would be a definite yes in C++, but I want to double check that I can do this in C# as well without introducing "hidden" stability problems, multi-threading problems or anything like that. In fact, C# should warn me in real-time if I used a wrong cast, but just I asked just to double check.)