Question

I have three classes, one class loads in a configuration file into memory for access later on. My other class is the mainform. What I am attempting to achieve is that when certain elements of the configuration class are loaded in they are added to a listview in the GUI (WindowsForm).

I know you can’t access the GUI directly from the other non-mainform classes, which after reading I don’t want to do anyway, so I have been attempting to fire events to say “config updated” that the mainform will listen for and update the listview when appropriate. So I created a third class that defines the events and the delegates etc but in all the examples I’ve seen if different classes are calling the event they are all passed a shared instance of the event class.

Is this the way I should do things? When I created the configuration class from the mainform class should I pass an instance of the event class? Or is there a way for 2 classes that don’t know anything about each other to share an event?

I’ve modified a microsoft example below to semi demonstrate what I’m needing.

    using System;

public class FireEventArgs : EventArgs
{
    public FireEventArgs(string room, int ferocity)
    {
        this.room = room;
        this.ferocity = ferocity;
    }
    public string room;
    public int ferocity;
}

public class FireAlarm
{
    public delegate void FireEventHandler(object sender, FireEventArgs fe);
    public event FireEventHandler FireEvent;

    public void ActivateFireAlarm(string room, int ferocity)
    {
        FireEventArgs fireArgs = new FireEventArgs(room, ferocity);
        if(FireEvent!=null)FireEvent(this, fireArgs);
    }
}

public class FireEventTest
{

    public static void ExtinguishFire(object sender, FireEventArgs fe)
    {

        Console.WriteLine("\nThe ExtinguishFire function was called by {0}.", sender.ToString());
        if (fe.ferocity < 2)
            Console.WriteLine("This fire in the {0} is no problem.  I'm going to pour some water on it.", fe.room);
        else if (fe.ferocity < 5)
            Console.WriteLine("I'm using FireExtinguisher to put out the fire in the {0}.", fe.room);
        else
            Console.WriteLine("The fire in the {0} is out of control.  I'm calling the fire department!", fe.room);
    }

    public static void Main()
    {
        FireAlarm myFireAlarm = new FireAlarm();
        FireAlarm fireAlarm = new FireAlarm();
        fireAlarm.FireEvent += new FireAlarm.FireEventHandler(ExtinguishFire);
        myFireAlarm.ActivateFireAlarm("Kitchen", 3);
        myFireAlarm.ActivateFireAlarm("Study", 1);
        myFireAlarm.ActivateFireAlarm("Porch", 5);
        return;

    }   
}

Thanks in advance for any help.

Answer 1

Well, I don’t think that I understand you fully, but you can have a class called EventDispatcher, make it Singleton if you want, and inside it have a public event

ConfigurationElementLoaded(object sender, ConfigurationElementLoadedArgs args)

and a public method to fire the event:

void FireConfigurationElementLoaded(ConfigurationElement element)

in which you fire the event.

Your mainForm can subscribe via the Singleton isntance : EventDispatcher.Instance.ConfigurationElementLoaded += ...

and your Configuration can fire the event with FireConfigurationElementLoaded.

If this answer doesn’t help, please elaborate more what exactly you want to do…