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Delegates & Events - (BCA / B.Tech)

Delegates & Events in .NET in Hindi | Introduction to Delegates and Events:

Delegates

Delegates in C# are a type of reference type that refers to a method.
In other words, delegates are used to refer to a method like a pointer. Delegates are used when we need to call a method at run-time.
Delegates are considered "type-safe" because they can only refer to methods whose signature (parameters and return type) matches the signature of the delegate.

Events

Events in C# are a mechanism based on delegates. Events are used when one class needs to inform another class about a particular situation.
For example, when a button is pressed, a "click" event is triggered.

To work with delegates and events, we need to follow these steps:

Define the delegate.
Create an object of the delegate.
Declare the event.
Subscribe to and trigger the event.
Simple program: Using delegates and events

Below is an example that explains delegates and events:

using System;

namespace DelegatesAndEventsExample

{

// Step 1: Define a delegate

public delegate void NotifyHandler(string message);

// Publisher class

public class Publisher

{

// Step 2: Declare an event using the delegate

public event NotifyHandler Notify;

public void TriggerEvent(string message)

{

// Step 3: Trigger the event

if (Notify != null)

{

Notify(message); // Notify all subscribers

}

// Subscriber class

public class Subscriber

{

public void OnNotifyReceived(string message)

{

Console.WriteLine("Subscriber received message: " + message);

}

class Program

{

static void Main(string[] args)

{

// Create publisher and subscriber objects

Publisher publisher = new Publisher();

Subscriber subscriber = new Subscriber();

// Step 4: Subscribe to the event

publisher.Notify += subscriber.OnNotifyReceived;

// Trigger the event

publisher.TriggerEvent("Hello, this is a test event!");

Console.ReadLine();

}

How it works:

A delegate named NotifyHandler was defined, which will refer to a method as a pointer.
An event Notify was declared in the Publisher class.
The OnNotifyReceived method was defined in the Subscriber class, which acts as an event handler.
In Main(), the Publisher event was subscribed to with the Subscriber's method and then the event was triggered.

Output:

Subscriber received message: Hello, this is a test event!

This example helps to explain delegates and events in a simple and practical way.

Delegates & Events

Delegates & Events in .NET in Hindi | Introduction to Delegates and Events:

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