Introduction
Delegates and events are important concepts in C# that enable different parts of an application to communicate cleanly and flexibly. Beginners often find these topics confusing at first, but once they understand them, they become powerful tools for writing clean, reusable, and maintainable code.
In simple terms, a delegate is like a reference to a method, and an event is a mechanism for notifying other parts of the program when something happens. In this article, we will explain delegates and events in C# step by step, using easy language and real-life examples.
What is a Delegate in C#?
A delegate in C# is a type that can hold a reference to a method. This means you can assign a method to a delegate and call that method using the delegate variable.
Think of a delegate as a remote control. The remote does not know how the TV works internally; it only knows which button to press. Similarly, a delegate does not know how a method is implemented; it only knows how to call it.
Delegates are useful when:
You want to pass methods as parameters
You want flexible and loosely coupled code
You want different methods to be called dynamically
Simple Delegate Example
Below is a simple example to understand how delegates work.
delegate void MessageDelegate(string message);
class Program
{
static void ShowMessage(string msg)
{
Console.WriteLine(msg);
}
static void Main()
{
MessageDelegate del = ShowMessage;
del("Hello from Delegate");
}
}
In this example:
MessageDelegate defines the method signature
ShowMessage matches the delegate signature
The delegate calls the method indirectly
This makes the code flexible and reusable.
Why Delegates Are Useful
Delegates help reduce tight coupling between classes. Instead of calling a method directly, one class can use a delegate to call any method that matches the required signature.
Example use cases:
Delegates make applications easier to extend and maintain.
What Is an Event in C#?
An event in C# is built on top of delegates. It is used to notify other parts of the program when something important happens.
In simple words, events follow the publish–subscribe model:
One class publishes an event
Other classes subscribe to that event
When the event occurs, all subscribers are notified
Real-life example: When a doorbell rings, everyone inside the house gets notified.
Simple Event Example
Let us understand events with a simple example.
class Alarm
{
public event Action AlarmTriggered;
public void Trigger()
{
Console.WriteLine("Alarm triggered");
AlarmTriggered?.Invoke();
}
}
class Program
{
static void Main()
{
Alarm alarm = new Alarm();
alarm.AlarmTriggered += OnAlarm;
alarm.Trigger();
}
static void OnAlarm()
{
Console.WriteLine("Notification received");
}
}
In this example:
The Alarm class defines an event
The Program class subscribes to the event
When the alarm triggers, subscribers are notified
Difference Between Delegates and Events
Although delegates and events are related, they are not the same.
Delegates:
Can be invoked directly
Are more flexible
Can be used anywhere
Events:
Are safer wrappers around delegates
Can only be triggered by the class that defines them
Are mainly used for notifications
In simple terms, delegates give control, while events give safety.
When to Use Delegates
Use delegates when:
You want to pass a method as a parameter
You need callback functionality
You want custom behavior at runtime
Example: Passing a validation method to a processing function.
When to Use Events
Use events when:
One class needs to notify multiple classes
You want loose coupling between components
You are building UI, notification, or monitoring systems
Example: Button click events, status change notifications, or background process alerts.
Delegates and Events in Real Applications
In real-world C# applications, delegates and events are widely used in:
They help build scalable and responsive systems.
Common Beginner Mistakes
Some common mistakes beginners make include:
Confusing delegates with events
Calling events directly from outside the class
Forgetting to check for null before invoking events
Understanding the basic purpose of each concept helps avoid these issues.
Summary
Delegates and events are powerful features in C# that enable flexible communication between different parts of an application. Delegates act as method references, allowing dynamic method calls, while events provide a safe and structured way to notify subscribers when something happens. By understanding and using delegates and events correctly, developers can write cleaner, more maintainable, and scalable C# applications.