Why delegates are needed in C Sharp (C#) - See It in Action

Understanding Why Delegates Are Needed in C#

📖 Scenario: Imagine you are building a simple notification system where different actions can be triggered when an event happens, like sending an email or logging a message.

🎯 Goal: You will create a delegate to hold references to methods and use it to call different actions dynamically. This shows why delegates are useful for flexible and reusable code.

📋 What You'll Learn

Create a delegate type called Notify that takes a string parameter and returns void

Create two methods called SendEmail and LogMessage that match the delegate signature

Create a variable of type Notify and assign it to SendEmail

Add LogMessage to the delegate invocation list

Invoke the delegate with a message string

Print the output of both methods being called

💡 Why This Matters

🌍 Real World

Delegates are used in event handling, callbacks, and designing flexible APIs where the exact method to run can change.

💼 Career

Understanding delegates is essential for C# developers to write clean, maintainable, and flexible code, especially in GUI apps and asynchronous programming.

1

Create the delegate type and methods

Create a delegate called Notify that takes a string parameter and returns void. Then create two methods called SendEmail and LogMessage that each take a string parameter and print messages starting with "Email sent:" and "Log entry:" respectively.

C Sharp (C#)

// Create delegate Notify
// Create methods SendEmail and LogMessage
// Your code here

Need a hint?

Delegates are like a type that can hold references to methods with a specific signature.

2

Create a delegate variable and assign a method

Inside the Program class, create a Notify variable called notifyHandler and assign it to the SendEmail method.

C Sharp (C#)

public delegate void Notify(string message);

public class Program
{
    public static void SendEmail(string message)
    {
        System.Console.WriteLine($"Email sent: {message}");
    }

    public static void LogMessage(string message)
    {
        System.Console.WriteLine($"Log entry: {message}");
    }

    public static void Main()
    {
        // Create Notify variable notifyHandler and assign SendEmail
        // Your code here
    }
}

Need a hint?

Assign a method name without parentheses to the delegate variable.

3

Add another method to the delegate invocation list

Add the LogMessage method to the notifyHandler delegate using the += operator so both methods will be called.

C Sharp (C#)

public delegate void Notify(string message);

public class Program
{
    public static void SendEmail(string message)
    {
        System.Console.WriteLine($"Email sent: {message}");
    }

    public static void LogMessage(string message)
    {
        System.Console.WriteLine($"Log entry: {message}");
    }

    public static void Main()
    {
        Notify notifyHandler = SendEmail;
        // Add LogMessage to notifyHandler
        // Your code here
    }
}

Need a hint?

Use += to add methods to the delegate's invocation list.

4

Invoke the delegate and print output

Call the notifyHandler delegate with the message "Hello World" inside Main to see both methods run and print their messages.

C Sharp (C#)

public delegate void Notify(string message);

public class Program
{
    public static void SendEmail(string message)
    {
        System.Console.WriteLine($"Email sent: {message}");
    }

    public static void LogMessage(string message)
    {
        System.Console.WriteLine($"Log entry: {message}");
    }

    public static void Main()
    {
        Notify notifyHandler = SendEmail;
        notifyHandler += LogMessage;
        // Invoke notifyHandler with "Hello World"
        // Your code here
    }
}

Need a hint?

Call the delegate like a method with the message string.