Why Delegates as callback pattern in C Sharp (C#)? - Purpose & Use Cases

The Big Idea

What if your program could call you back exactly when it's ready, without you waiting or checking?

The Scenario

Imagine you are building a program that needs to perform a task, then notify you when it's done. Without delegates, you might write separate code for each notification, making your program bulky and hard to change.

The Problem

Manually checking if a task is done or writing many specific methods for each notification is slow and error-prone. It's like having to call each friend individually to tell them the same news instead of sending one message that everyone can get.

The Solution

Delegates let you pass a method as a parameter, so your program can call back any function you want when a task finishes. This makes your code cleaner, flexible, and easy to update--like sending one message that automatically reaches the right people.

Before vs After

✗ Before

void TaskDone() { NotifyUser(); LogCompletion(); }
void NotifyUser() { /* code */ }
void LogCompletion() { /* code */ }

✓ After

delegate void Callback();
void DoTask(Callback cb) { /* work */ cb(); }
DoTask(() => Console.WriteLine("Task finished!"));

What It Enables

It enables your program to flexibly react to events by calling different methods without changing the main task code.

Real Life Example

Think of ordering food delivery: you place an order (task), then get a call, text, or app notification (callback) when it arrives, depending on your preference.

Key Takeaways

Manual notification methods are rigid and repetitive.

Delegates let you pass methods as parameters for flexible callbacks.

This pattern keeps code clean and easy to update.