事件传递参数

Question

I have problem with event. For example let i have event public event EventHandler<AxisChangedEventArgs> AxisChanged which fires when Axis pan or zoom or something else. When it's firing i am making Console.WriteLine("Working"); . How can i pass CFDBOX parameter into SomeWork anonymous method does not help because it will be imposible to unsubscribe from it. And i cannot override AxisChanged event.

public void AddEvents(CFDBOX CFDBOX) {
    CFDBOX.PlotModel.Axes[0].AxisChanged += SomeWork;
}

public void RemoveEvents(CFDBOX CFDBOX) {
    CFDBOX.PlotModel.Axes[0].AxisChanged -= SomeWork;
}

public EventHandler<AxisChangedEventArgs> SomeWork =
    delegate(object o, AxisChangedEventArgs args) {
        Console.WriteLine("Working");
    }
;

Answer 1

Take advantage of closure lambda expressions:

private EventHandler<AxisChangedEventArgs> axisChangedEventHandler;

public void AddEvent(CFDBOX CFDBOX) {
    // keep a reference of the event handler to remove it later
    axisChangedEventHandler = (o, args) => {
        // parameter CFDBOX bound to the event handler
        Console.WriteLine("Working " + CFDBOX); 
    };
    // register event handler
    CFDBOX.PlotModel.Axes[0].AxisChanged += axisChangedEventHandler;
}

public void RemoveEvent() {
    // unregister event handler
    CFDBOX.PlotModel.Axes[0].AxisChanged -= axisChangedEventHandler;
}

Answer 2

Any parameter which must be passed with an event should be a member of your EventArgs implementation. In your scenario: AxisChangedEventArgs . Hope i get your question.

The sender of the event (in your case o ) should always be the instance, which calls the event. So if your event get's fired from different classes (not instances!), you will have to check for the type of o .