Introduction to Delegates

Vaibhav • September 11, 2025

Delegates are one of the most powerful and flexible features in C#. They allow you to treat methods as first-class objects - meaning you can pass them around, store them, and invoke them dynamically. If you’ve ever wanted to call a method without knowing its name at compile time, or allow users to plug in their own logic, delegates are the tool for the job.

In this article, we’ll explore what delegates are, why they matter, and how they fit into the broader picture of functional programming. We’ll start with the basics and build up to real-world usage patterns, all while staying grounded in the concepts you’ve already learned - like methods, parameters, and object-oriented design.

What is a Delegate?

A delegate is a type that represents references to methods with a specific signature. Think of it as a method pointer - but safer and more powerful. You define a delegate type, and then you can assign any method that matches its signature to a variable of that type.

Declaring a Delegate Type

Let’s start by declaring a simple delegate that takes two integers and returns an integer:

public delegate int Operation(int x, int y);

This defines a new type called Operation. Any method that takes two int parameters and returns an int can be assigned to a variable of this type.

Assigning Methods to Delegates

Once you’ve declared a delegate type, you can assign methods to it. Here’s a simple example:

int Add(int a, int b)
{
    return a + b;
}

Operation op = Add;
Console.WriteLine(op(3, 4)); // Output: 7

The method Add matches the signature of Operation, so it can be assigned directly. When you invoke op(3, 4), it calls Add with those arguments.

Why Use Delegates?

Delegates shine when you want to decouple logic. For example, you might write a sorting algorithm that accepts a comparison delegate, allowing callers to define their own sorting rules. Or you might build a UI framework where button clicks are handled by delegate callbacks.

Delegates vs Methods

You might wonder - why not just call methods directly? The answer lies in flexibility. With delegates, you can:

• Store methods in variables
• Pass methods as parameters
• Invoke methods dynamically
• Chain multiple methods together (multicast)

This opens the door to plug-in architectures, event-driven systems, and functional-style programming.

Real-World Analogy

Imagine a coffee machine that accepts different brewing strategies. Instead of hardcoding the brewing logic, you define a delegate called BrewStrategy. Now users can plug in their own brewing methods - espresso, drip, cold brew - without changing the machine’s code.

public delegate void BrewStrategy();

void Espresso() => Console.WriteLine("Brewing espresso...");
void ColdBrew() => Console.WriteLine("Brewing cold brew...");

BrewStrategy strategy = Espresso;
strategy(); // Output: Brewing espresso...

strategy = ColdBrew;
strategy(); // Output: Brewing cold brew...

This pattern is common in frameworks, libraries, and APIs that want to be extensible and user-configurable.

Delegates and Type Safety

One of the key advantages of delegates is type safety. The compiler ensures that only methods with the correct signature can be assigned. This prevents runtime errors and makes your code more robust.

Delegates and Object-Oriented Design

Delegates complement object-oriented design by allowing behavior to be passed around like data. Instead of subclassing or overriding methods, you can inject behavior via delegates. This leads to cleaner, more modular code.

For example, a logging system might accept a delegate for formatting messages. Different modules can supply their own formatters without modifying the core logger.

Summary

Delegates are a cornerstone of flexible, extensible C# programming. They allow you to treat methods as data - passing them around, storing them, and invoking them dynamically. In this article, we introduced the concept of delegates, showed how to declare and use them, and explored their role in real-world design.

You now understand how delegates enable decoupling, extensibility, and functional-style programming. In the next article, we’ll dive deeper into Delegate Declaration and Usage, exploring parameterized delegates, return types, and practical usage patterns.