using System;

public class Program

{

    public static void Main()

    {

        ProcessBusinessLogic bl = new ProcessBusinessLogic();

                Test bl2 = new Test();

        bl.ProcessCompleted += bl_ProcessCompleted; // register with an event

        bl.StartProcess();

    }

​

    // event handler

    public static void bl_ProcessCompleted(object sender, EventArgs e)

    {

        Console.WriteLine("I changed item2 to red");

    }

}

​

public class Test

{

    public Test()

    {

        ProcessBusinessLogic bl = new ProcessBusinessLogic();

        bl.ProcessCompleted += bl_ProcessCompleted; // register with an event

        bl.StartProcess();

    }

​

    // event handler

    public static void bl_ProcessCompleted(object sender, EventArgs e)

    {

        Console.WriteLine("I changed item1 to blue!");

    }

}

public class ProcessBusinessLogic

{

    public event EventHandler ProcessCompleted; // event

​

    public void StartProcess()

    {

        Console.WriteLine("Started the event!");

        // some code here..

        OnProcessCompleted(EventArgs.Empty);

    }

​

​

    protected virtual void OnProcessCompleted(EventArgs e)

    {

        ProcessCompleted?.Invoke(this, e);

    }

}