Event, Delegate, EventArgs in .Net Framework. A example of Observer Design Pattern in Unity3D c#

Alert.cs

using UnityEngine;
using System.Collections;


/// <summary>
/// Observer or subscriber in Observe Design Pattern
/// It register(or subscribe) Boiled event in Heater at Main::Start(). When water boiled, 
/// it receives BoiledEventArgs and Object sender. Do logic base on those received data.
/// </summary>
public class Alert : MonoBehaviour {
    public void DoAlarm(Object sender, BoiledEventArgs e)
    {
        Heater heater = (Heater)sender;
        Debug.Log("Alarm >> Temprature is " + e.temperature + "(Made in " + heater.MADE_IN + " Model is " + heater.MODEL + ")");
    }
}

Heater.cs

using UnityEngine;
using System.Collections;

/// <summary>
/// Subject or publisher in Observe Design Pattern
/// There is a Event named Boiled. When its temperature reach to 95, it will publish that event
/// to observers, which are Alert and UI_Displayer.
/// </summary>
public class Heater : MonoBehaviour {
    // Other value the event can get by Object sender.
    public readonly string MODEL = "RealFire_MC20";
    public readonly string MADE_IN = "CHINA";

    // Delegate and Event
    public delegate void BoiledEventHandler(Object sender, BoiledEventArgs e);
    public event BoiledEventHandler Boiled;

    // Value event can get by BoiledEventAregs e
    private int temperature;

    // Boil water
    public void BoilWater()
    {
        for (int i = 0; i < 100; i++)
        {
            temperature = i;

            if (temperature >= 97)
            {
                // Create EventArgs, contains temperature value.
                BoiledEventArgs e = new BoiledEventArgs(temperature);
                OnBoiled(e);
            }
        }
    }

    // Generate Boiled event
    protected virtual void OnBoiled(BoiledEventArgs e)
    {
        if(Boiled != null)
        {
            Boiled(this, e);
        }
    }
}

/// <summary>
/// Customised EventArgs
/// </summary>
public class BoiledEventArgs : System.EventArgs
{
    // Can contains other values.
    public readonly int temperature;
    public BoiledEventArgs(int temperature)
    {
        this.temperature = temperature;
    }
}

Main.cs

using UnityEngine;
using System.Collections;

/// <summary>
/// Main. Observers subscribe event here. Boil water.
/// </summary>
public class Main : MonoBehaviour {
    public Heater heater;
    public Alert alert;

	// Use this for initialization
	void Start () {
        // Assign event
        heater.Boiled += alert.DoAlarm; // 1st way to assign event.
        heater.Boiled += (new Alert()).DoAlarm; // 2nd way to assign event.
        heater.Boiled += new Heater.BoiledEventHandler(alert.DoAlarm); // 3rd way to assign event.
        heater.Boiled += UI_Displayer.ShowMsg;  // By a static method.

        // Do boil water
        heater.BoilWater();
	}
}

UI_Displayer.cs

using UnityEngine;
using System.Collections;

/// <summary>
/// Observer or subscriber in Observe Design Pattern
/// It register(or subscribe) Boiled event in Heater at Main::Start(). When water boiled, 
/// it receives BoiledEventArgs and Object sender. Do logic base on those received data.
/// </summary>
public class UI_Displayer : MonoBehaviour {

    public static void ShowMsg(Object sender, BoiledEventArgs e)
    {
        Heater heater = (Heater)sender;
        Debug.Log("UI_Displayer >> Alarm: temprature is " + e.temperature + "(Made in " + heater.MADE_IN + " Model is " + heater.MODEL + ")");
    }

}