Events in C# Programming

Events in C# are mechanisms that allow a class to notify other classes or objects when something of interest occurs. Events rely on delegates to define and raise notifications.

1. Defining and Raising Events

To define and raise an event, you need a delegate type and an event based on that delegate.

Step-by-Step Example: Defining and Raising Events

    using System;
   // Define a delegate
    delegate void Notify(string message);
   // Define a class with an event
    class EventPublisher {
        public event Notify OnNotify;
       public void RaiseEvent(string message) {
            // Check if there are any subscribers
            if (OnNotify != null) {
                OnNotify(message);
            }
        }
    }
   class Program {
        static void Main() {
            EventPublisher publisher = new EventPublisher();
           // Subscribe to the event
            publisher.OnNotify += (msg) => Console.WriteLine("Event raised: " + msg);
           // Raise the event
            publisher.RaiseEvent("Hello, Events!");
        }
    }

Output:

Event raised: Hello, Events!

2. Event Handling

Event handling involves subscribing to an event and defining the actions to be performed when the event is triggered.

Step-by-Step Example: Event Handling

    using System;
   // Define a delegate
    delegate void Notify(string message);
   // Define a class with an event
    class Alarm {
        public event Notify AlarmTriggered;
       public void TriggerAlarm(string location) {
            if (AlarmTriggered != null) {
                AlarmTriggered("Alarm triggered at: " + location);
            }
        }
    }
   class Program {
        // Event handler method
        static void HandleAlarm(string message) {
            Console.WriteLine(message);
        }
       static void Main() {
            Alarm alarm = new Alarm();
           // Subscribe to the event
            alarm.AlarmTriggered += HandleAlarm;
           // Raise the event
            alarm.TriggerAlarm("Server Room");
        }
    }

Output:

Alarm triggered at: Server Room

Key Points

  • Events are special delegates designed for one-to-many notifications.
  • Events ensure encapsulation by only allowing the event publisher to raise the event.
  • Subscribers can register or unregister from events dynamically.

Conclusion

Events in C# are integral to building event-driven and interactive applications. By defining and handling events, developers can create programs that respond dynamically to user actions or system changes.



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