A well explained example on events in C#, the example taken as it is from the book Mastering Visual C#.NET

EventsInCSharp_FullExample.cs

/*
Example12_4.cs illustrates the use of an event
*/
using System;
// declare the MeltdownEventArgs class (implements EventArgs)
public class MeltdownEventArgs : EventArgs
{
    // declare a private field named message
    private string message;
    // define a constructor
    public MeltdownEventArgs(string message)
    {
        this.message = message;
    }
    // define a property to get the message
    public string Message
    {
        get
        {
            return message;
        }
    }
}
// declare the Reactor class
public class Reactor
{
    // declare a private field named temperature
    private int temperature;
    // declare a delegate class named MeltdownHandler
    public delegate void MeltdownHandler(
    object reactor,
    MeltdownEventArgs myMEA
    );
    // declare an event named OnMeltdown
    public event MeltdownHandler OnMeltdown;
    // define a property to set the temperature
    public int Temperature
    {
        set
        {
            temperature = value;
            // if the temperature is too high, the reactor melts down
            if (temperature > 1000)
            {
                MeltdownEventArgs myMEA =
                new MeltdownEventArgs("Reactor meltdown in progress!");
                OnMeltdown(this, myMEA);
            }
        }
    }
}
// declare the ReactorMonitor class
public class ReactorMonitor
{
    // define a constructor
    public ReactorMonitor(Reactor myReactor)
    {
        myReactor.OnMeltdown +=
        new Reactor.MeltdownHandler(DisplayMessage);
    }
    // define the DisplayMessage() method
    public void DisplayMessage(
    object myReactor, MeltdownEventArgs myMEA
    )
    {
        Console.WriteLine(myMEA.Message);
    }
}
class Example12_4
{
    public static void Main()
    {
        // create a Reactor object
        Reactor myReactor = new Reactor();
        // create a ReactorMonitor object
        ReactorMonitor myReactorMonitor = new ReactorMonitor(myReactor);
        // set myReactor.Temperature to 100 degrees Centigrade
        Console.WriteLine("Setting reactor temperature to 100 degrees Centigrade");
        myReactor.Temperature = 100;
        // set myReactor.Temperature to 500 degrees Centigrade
        Console.WriteLine("Setting reactor temperature to 500 degrees Centigrade");
        myReactor.Temperature = 500;
        // set myReactor.Temperature to 2000 degrees Centigrade
        // (this causes the reactor to meltdown)
        Console.WriteLine("Setting reactor temperature to 2000 degrees Centigrade");
        myReactor.Temperature = 2000;
    }
}
/*The output from this program is as follows:
Setting reactor temperature to 100 degrees Centigrade
Setting reactor temperature to 500 degrees Centigrade
Setting reactor temperature to 2000 degrees Centigrade
Reactor meltdown in progress!*/