Custom Events in C#

What  is an event? we can say , event is an  "Occurrence happening at a determinable time”. It can be anything, such as function, party, anything.

Let us take an easy example, 

One fine day, you are returning to your home from the playground.  Once reached the home,  you felt like starving(not just hungry). And so you reached the kitchen to have some food. Unfortunately the food is not yet prepared (told by your mom). So you went to your bedroom to kill some time, until the food gets ready. Later, you need to know immediately, once the food is prepared. 

Where "preparing food" is an event, once it is prepared it will be notified by your mom (EventHandler). So an event handler is alone enough to get notified ? Oh. Wait.

What if your bedroom is in the first floor and kitchen is in the ground floor. On that case, you will be notified through mobile phone, right? (why not?). So you need two more mobiles. OK, lets summarise here, the five major key elements which are responsible 

• Event (food preparation)
• Event Handler(To notify)
• Publisher (to send)
• Subscriber (to receive)
• Arguments (Details)

1.Event

You need to get notified once the food is ready.

2.Event Handler

Of course, handler is needed to notify you. (where the name of this delegate will be the type of the event, matching colours.)

3.Publisher (your mom’s mobile)

From which the notifications will be published to all its subscriber. (yes it can be subscribed by many subscribes,  which mean your brother will also get notified along with you :p )

4.Subscriber

Are we miss something, hmm?, yes the arguments (details).

5.Arguments

Create a separate class for the details you needed. Here i need to know whether the food prepared is vegetarian or not, also how many varieties of dishes are available. You can add as many as properties based on your need.

So now, the system is ready, late take a look at the kitchen. 

public class Kitchen
    {
       public Kitchen()
        {
          MakeFood();
        }

        public void MakeFood()
        {
         
          FoodDetailsEventArgs  args = new FoodDetailsEventArgs();
   args.TotalDishes = 4;
  args.IsVeg = False;
          OnFoodPrepared(args);  
        }

     public event  FoodPreparationEventHandler FoodPrepared;
    
public delegate void FoodPreparationEventHandler(FoodDetailsEventArgs e);

public class FoodDetailsEventArgs : EventArgs
    {
        public int TotalDishes { get; set; }
        public bool IsVeg { get; set; }
    }
protected virtual void OnFoodPrepared(FoodDetailsEventArgs e)
   {
     FoodPreparationEventHandler handler = FoodPrepared;
     if (handler != null)
       {
          handler(this, e);
       }
   }
}

Now, let see your bedroom (NO, I meant the class name :p ), 

public class BedRoom
{
  Kitchen kitchen;
  public BedRoom()
    {
      kitchen = new Kitchen();
      kitchen.FoodPrepared += FoodReady;
    }
  static void FoodReady(FoodDetailsEventArgs e)
    {
     Person.RunToDinningTable(); 
    }
}

I guess, you won’t understand anything from the above article, In that case refer the MSDN link.

Happy Coding.

Joy Rex.