一个班级的Mouse Event，如何在另一个班级听呢？

Question

I have a UserControl on a Form, when I MouseMove on that UserControl I want to do something in the Form.

How can I make the Form 'listen' for this event?

I am using Visual C#, .Net framework 3.5, winforms

Answer 1

I suppose you're referring to a use control or something like that.

You can add a public event , and trigger it inside your class when detecting the inner class event.

Then you have to subscribe to the published event in the second class.

This is a sample so that you see the sintax:

    public class WithEvent
    {
        // this is the new published event
        public EventHandler<EventArgs> NewMouseEvent;

        // This handles the original mouse event of the inner class
        public void OriginalEventhandler(object sender, EventArgs e)
        {
            // this raises the published event (if susbcribedby any handler)
            if (NewMouseEvent != null)
            {
                NewMouseEvent(this, e);
            }
        }
    }

    public class Subscriber
    {
        public void Handler(object sender, EventArgs e)
        {
            // this is the second class handler
        }

        public void Subscribe()
        {
            WithEvent we = new WithEvent();
            // This is how you subscribe the handler of the second class
            we.NewMouseEvent += Handler;
        }

    }

Answer 2

If you are talking about Windows Forms (it's not clear from the question) you need to define a new event in the class who recieves the mouse-event. After reciving it raises a new custom-event. Another class is subcribed to that (custom-event) a recieves notification.

For moe information (it's not something that can be presenteed in a couple of lines) can have alook here:

How to propagate an Event up to the MainForm?

If you are talking about WPF , there are different concept of events: event routing. If your class is UI element present in UI tree of the component that recieves actually mouse-event, it will be propagated to your class too. So no need of more coding.

Answer 3

To expand a little on the answer from JotaBe, there are two scenarios that I could see you having:

a) class A calls a method in class B, and an exception happens. In this case, you don't need to do anything: exception will walk the stack, until it finds a catch statement. So, really, all you need to do is NOT catch an exception, or if you do need to catch it (for logging purposes and such), then rethrow it.

b) if you need to have a code triggered in some unrelated class, as a result of exception, then the best way is to use events. In your class declare:

public class ClassA
{
    public static event EventHandler<Exception> OnException;

    public void Notify(Exception ex)
    {
        if (OnException != null)
        {
            OnException(this, ex);
        }
    }
}

and then, in order to be notified, all you need is to

ClassA.OnException += (sender, exeption) => 
{
    ... some GetHashCode ..
};

... I guess JotaBe already added all necessary example code as I was typing