Delegates vs Interfaces in C#

Delegates and interfaces are both powerful constructs in C# that allow for flexible and extensible code. While they serve different purposes, they can sometimes be used to achieve similar ends, leading to confusion about when to use one over the other. This article will elucidate the differences and similarities between delegates and interfaces, and provide guidelines for their use.

Understanding Delegates in C#

A delegate in C# is a type that defines a method signature, and can hold a reference to a method. When a delegate is invoked, it calls the method it references. This provides a way to pass methods as parameters, a feature commonly used in event handling and callbacks.


Here's a simple example of a delegate −

using System;

public delegate void DisplayMessage(string message);

public class Program {
   static void Main(string[] args) {
      DisplayMessage dm = Console.WriteLine;
      dm("Hello, World!");

In this example, the delegate DisplayMessage holds a reference to Console.WriteLine, and invoking dm calls Console.WriteLine.


Hello, World!

Understanding Interfaces in C#

An interface in C# is a contract that defines a set of methods, properties, and events. Any class or struct that implements the interface must provide an implementation for all of its members.


Here's a simple example of an interface −

using System;

public interface IDisplayMessage {
   void Display(string message);

public class ConsoleDisplay : IDisplayMessage {
   public void Display(string message) {

public class Program {
   static void Main(string[] args) {
      IDisplayMessage display = new ConsoleDisplay();
      display.Display("Hello, World!");

In this example, ConsoleDisplay implements the IDisplayMessage interface and provides an implementation for the Display method.


Hello, World!

Delegates vs Interfaces

While delegates and interfaces can sometimes be used to achieve similar goals, they have key differences −





Pass methods as parameters and manage groups of methods (event handling, callbacks)

Define contracts with methods, properties, and events

Method Chaining

Can chain multiple methods together

Not supported


Not supported

Supports inheritance

Multiple Behaviors

Not supported

Can implement multiple behaviors in a class or struct


Defines method signature, holds method reference

Contract containing method, property, and event declarations

Usage Scenario

Event handling, callbacks

Defining a set of related methods and properties for classes or structs to implement


Can be extended with multicast delegates

Can be extended with inheritance


Supports covariance and contravariance

Does not support variance

In general, use a delegate when you need to pass a method as a parameter or manage a group of methods as an entity (like in event handling). Use an interface when you want to define a contract that classes or structs can implement.


Understanding the differences and similarities between delegates and interfaces is crucial for writing effective and efficient C# code. While both offer powerful ways to manage methods, knowing when to use one over the other can lead to more readable and maintainable code.

Updated on: 24-Jul-2023


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