Multicast delegates in C Sharp (C#) - Mini Project: Build & Apply

Multicast delegates

📖 Scenario: Imagine you are building a simple notification system where multiple actions happen when an event occurs, like sending an email and logging a message.

🎯 Goal: You will create a multicast delegate that calls multiple methods when invoked, demonstrating how multicast delegates work in C#.

📋 What You'll Learn

Create a delegate type named Notify that takes no parameters and returns void

Create two methods named SendEmail and LogMessage that print specific messages

Create a multicast delegate instance combining SendEmail and LogMessage

Invoke the multicast delegate to see both messages printed

💡 Why This Matters

🌍 Real World

Multicast delegates are useful in event handling systems where multiple actions need to respond to a single event, such as UI updates, logging, and notifications.

💼 Career

Understanding multicast delegates helps in building responsive and modular C# applications, especially in desktop, web, and game development.

1

Create the delegate type and methods

Create a delegate type called Notify that takes no parameters and returns void. Then create two methods: SendEmail that prints "Email sent." and LogMessage that prints "Message logged."

C Sharp (C#)

// Create delegate type Notify
// Create method SendEmail that prints "Email sent."
// Create method LogMessage that prints "Message logged."

Need a hint?

Use delegate void Notify() to declare the delegate type. Methods must match this signature.

2

Create a multicast delegate instance

Inside the Main method, create a variable called notifyHandlers of type Notify and assign it to SendEmail. Then add LogMessage to notifyHandlers using the += operator.

C Sharp (C#)

using System;

public delegate void Notify();

class Program
{
    public static void SendEmail()
    {
        Console.WriteLine("Email sent.");
    }

    public static void LogMessage()
    {
        Console.WriteLine("Message logged.");
    }

    static void Main()
    {
        // Create Notify variable notifyHandlers and assign SendEmail
        // Add LogMessage to notifyHandlers
    }
}

Need a hint?

Use Notify notifyHandlers = SendEmail; and then notifyHandlers += LogMessage; to combine methods.

3

Invoke the multicast delegate

Still inside the Main method, invoke the notifyHandlers delegate to call both SendEmail and LogMessage methods.

C Sharp (C#)

using System;

public delegate void Notify();

class Program
{
    public static void SendEmail()
    {
        Console.WriteLine("Email sent.");
    }

    public static void LogMessage()
    {
        Console.WriteLine("Message logged.");
    }

    static void Main()
    {
        Notify notifyHandlers = SendEmail;
        notifyHandlers += LogMessage;
        // Invoke notifyHandlers
    }
}

Need a hint?

Call the delegate like a method: notifyHandlers();

4

Display the output

Run the program and observe the output. It should print both "Email sent." and "Message logged." lines.

C Sharp (C#)

using System;

public delegate void Notify();

class Program
{
    public static void SendEmail()
    {
        Console.WriteLine("Email sent.");
    }

    public static void LogMessage()
    {
        Console.WriteLine("Message logged.");
    }

    static void Main()
    {
        Notify notifyHandlers = SendEmail;
        notifyHandlers += LogMessage;
        notifyHandlers();
        // Output is shown automatically
    }
}

Need a hint?

Both messages should appear one after the other when you run the program.