Event declaration syntax in C Sharp (C#) - Mini Project: Build & Apply

Event Declaration Syntax in C#

📖 Scenario: You are building a simple notification system where a class can notify others when an event happens.

🎯 Goal: Create a class with an event declaration and trigger the event to notify subscribers.

📋 What You'll Learn

Declare an event using the event keyword

Use a delegate type EventHandler for the event

Create a method to raise the event

Subscribe to the event and handle it by printing a message

💡 Why This Matters

🌍 Real World

Events are used in user interfaces, game programming, and many applications to notify parts of a program when something happens.

💼 Career

Understanding event declaration and handling is essential for C# developers working on desktop apps, web apps, and game development.

1

Create a class with an event declaration

Create a class called Notifier and declare an event called OnNotify using the delegate type EventHandler.

C Sharp (C#)

public class Notifier
{
    // Declare the event here
    // Your code here
}

Need a hint?

Use public event EventHandler OnNotify; inside the class.

2

Add a method to raise the event

Inside the Notifier class, add a public method called Notify that raises the OnNotify event if it has subscribers.

C Sharp (C#)

using System;

public class Notifier
{
    public event EventHandler OnNotify;

    // Add Notify method here
    // Your code here
}

Need a hint?

Use the null-conditional operator ?. to safely invoke the event.

3

Subscribe to the event and handle it

Create a Main method. Inside it, create an instance of Notifier called notifier. Subscribe to the OnNotify event with a lambda that prints "Event triggered!".

C Sharp (C#)

using System;

public class Notifier
{
    public event EventHandler OnNotify;

    public void Notify()
    {
        OnNotify?.Invoke(this, EventArgs.Empty);
    }
}

public class Program
{
    public static void Main()
    {
        // Create notifier instance
        // Subscribe to OnNotify event
        // Your code here
    }
}

Need a hint?

Use notifier.OnNotify += (sender, e) => Console.WriteLine("Event triggered!"); to subscribe.

4

Trigger the event and display the output

In the Main method, after subscribing, call the Notify method on notifier to trigger the event and print the message.

C Sharp (C#)

using System;

public class Notifier
{
    public event EventHandler OnNotify;

    public void Notify()
    {
        OnNotify?.Invoke(this, EventArgs.Empty);
    }
}

public class Program
{
    public static void Main()
    {
        Notifier notifier = new Notifier();
        notifier.OnNotify += (sender, e) => Console.WriteLine("Event triggered!");
        // Call Notify method here
        // Your code here
    }
}

Need a hint?

Call notifier.Notify(); to raise the event and see the message.