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Home Forums What is a delegate? How is it different from an event? – MindStick
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1 Answers

Anubhav Sharma
Anubhav Sharma 28 May 2026
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In languages like C#, both delegates and events are used for handling methods dynamically and enabling communication between objects. They are closely related, but they serve different purposes.

What is a Delegate?

A delegate is a type-safe function pointer.

It stores a reference to a method and allows you to call that method indirectly.

You can think of a delegate as:

“A variable that can hold a method.”

Delegate Syntax

// Declare delegate
public delegate void MessageDelegate(string message);

This delegate can store any method that:

Returns void

Accepts a string parameter

Delegate Example

// Import namespace
using System;

class Program
{
    // Create delegate
    public delegate void PrintDelegate(string text);

    // Method matching delegate signature
    static void PrintMessage(string message)
    {
        // Print message
        Console.WriteLine(message);
    }

    static void Main()
    {
        // Store method inside delegate
        PrintDelegate pd = PrintMessage;

        // Invoke method using delegate
        pd("Hello Delegate");
    }
}

Output:

Hello Delegate

What is an Event?

An event is a wrapper around a delegate that provides controlled access.

Events are used for:

  • Notifications
  • Callbacks
  • Observer pattern
  • UI interactions

Example:

  • Button click
  • Mouse movement
  • File download completed

Event Syntax

// Declare event
public event MessageDelegate OnMessage;

Here:

  • MessageDelegate is the delegate type
  • OnMessage is the event

Event Example

// Import namespace
using System;

class Publisher
{
    // Declare delegate
    public delegate void Notify(string message);

    // Declare event
    public event Notify OnNotify;

    // Trigger event
    public void RaiseEvent()
    {
        // Check if event has subscribers
        if (OnNotify != null)
        {
            // Fire event
            OnNotify("Event Triggered");
        }
    }
}

class Program
{
    // Event handler method
    static void ShowMessage(string msg)
    {
        // Print message
        Console.WriteLine(msg);
    }

    static void Main()
    {
        // Create publisher object
        Publisher pub = new Publisher();

        // Subscribe to event
        pub.OnNotify += ShowMessage;

        // Trigger event
        pub.RaiseEvent();
    }
}

Output:

Event Triggered

Key Difference Between Delegate and Event

Feature Delegate Event
Purpose Store/call methods Notify subscribers
Access Can be invoked directly Can only be invoked inside declaring class
Usage Method references Publisher-subscriber pattern
Encapsulation Less secure More secure
Operators Assignment allowed Only += and -= outside class
Typical Use Callbacks, strategy pattern UI events, notifications

Important Concept

A delegate is like:

“Holding a phone number.”

An event is like:

“Subscribing to a notification service.”

Why Events are Safer

With delegates:

// Dangerous: external code can overwrite delegate
myDelegate = null;

With events:

// Only subscription allowed
myEvent += Handler;

External classes cannot directly trigger or reset the event.

Only the owner class can invoke it.

Relationship Between Delegate and Event

Events are built on top of delegates.

Internally:

public event Notify OnNotify;

uses a delegate behind the scenes.

So:

Delegate = foundation

Event = controlled notification mechanism

Real-World Example

Delegate

A delegate is like:

  • Saving a contact number
  • Calling the contact anytime

Event

An event is like:

  • You subscribe to YouTube notifications
  • Creator uploads video
  • You receive notification automatically

Built-in Delegates in C#

C# already provides common delegates:

Action

// No return value
Action<string> action = PrintMessage;

Func

// Returns value
Func<int, int, int> add = (a, b) => a + b;

Predicate

// Returns bool
Predicate<int> isEven = x => x % 2 == 0;

When to Use Delegate

Use delegates when:

  • Passing methods as parameters
  • Creating callbacks
  • Implementing strategy pattern

When to Use Event

Use events when:

  • One object should notify many objects
  • Building UI applications
  • Creating observer-based systems
  • Handling asynchronous notifications

Summary

Delegate

  • Stores method references
  • Can invoke methods dynamically
  • Similar to function pointers

Event

  • Built on delegates
  • Provides controlled notifications
  • Supports publisher-subscriber pattern

Most real-world C# applications use events extensively for communication between components.

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