🛠️ Understanding Dependency Injection in C#: A Simple Guide for Beginners

 

🤔 What is Dependency Injection?

Let’s break it down with an everyday example.

🎯 Real-World Scenario: Ordering Pizza 🍕

Imagine you love pizza, and every time you want one, you go to a specific pizza shop (hardcoded dependency).

public class Person
{
    private PizzaShop _pizzaShop = new PizzaShop(); // Direct dependency

    public void OrderPizza()
    {
        _pizzaShop.MakePizza();
    }
}

🛑 Problem:

• You are tied to one pizza shop (class PizzaShop).
• What if you want to order from a different pizza shop?
• What if the pizza shop closes?

✅ Solution: Dependency Injection (DI)

Instead of hardcoding the pizza shop, let's allow any pizza provider to be used.

public interface IPizzaProvider
{
    void MakePizza();
}

public class DominoPizza : IPizzaProvider
{
    public void MakePizza() => Console.WriteLine("Making Pizza from Domino's...");
}

public class Person
{
    private readonly IPizzaProvider _pizzaProvider;

    public Person(IPizzaProvider pizzaProvider)
    {
        _pizzaProvider = pizzaProvider; // Dependency is injected
    }

    public void OrderPizza()
    {
        _pizzaProvider.MakePizza();
    }
}

Now, we can easily switch pizza providers:

Person person = new Person(new DominoPizza());
person.OrderPizza();

🎉 Now, the person can order from any pizza provider without changing their code!

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🤔 Why Use Dependency Injection?

✅ Flexibility – Easily switch between different implementations.
✅ Testability – Makes unit testing easy (mock dependencies).
✅ Maintainability – No need to modify code when adding new services.

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🔧 Using Dependency Injection in C# with .NET Core

C# provides built-in dependency injection with the IServiceCollection.

Step 1: Define Interfaces & Implementations

public interface IPizzaProvider
{
    void MakePizza();
}

public class DominoPizza : IPizzaProvider
{
    public void MakePizza() => Console.WriteLine("Making Pizza from Domino's...");
}

public class PizzaHut : IPizzaProvider
{
    public void MakePizza() => Console.WriteLine("Making Pizza from Pizza Hut...");
}

Step 2: Register Dependencies in DI Container

var services = new ServiceCollection();
services.AddTransient<IPizzaProvider, DominoPizza>();

var serviceProvider = services.BuildServiceProvider();

Step 3: Inject Dependency and Use the Service

var pizzaProvider = serviceProvider.GetService<IPizzaProvider>();
pizzaProvider.MakePizza();  // Outputs: "Making Pizza from Domino's..."

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🎯 Final Thoughts

Dependency Injection is like ordering food from any restaurant instead of being stuck with one. 🍕🍔

• It makes code more modular, testable, and maintainable.
• It is widely used in ASP.NET Core, Web APIs, and microservices.

💡 What do you think? Have you used DI in your projects? Let me know in the comments! 😊