Dependency Injection Examples in .NET

This repository demonstrates Dependency Injection (DI) in .NET using two separate projects:

• ConsoleAppDI/: A lightweight console application that manually sets up DI.
• WebApiDI/: An ASP.NET Core Web API project that leverages built-in DI features.

The goal is to showcase how DI can help build loosely coupled, maintainable, and testable applications in both minimal and full-featured .NET environments.

📝 These examples are also explained in detail in the blog post:
👉 Read the blog post here!

🗂️ Project Structure

.
├── ConsoleAppDI/
├── WebApiDI/
├── dependency-injection.sln
└── README.md

💡 About Dependency Injection

Dependency Injection is a software design pattern that allows a class to receive its dependencies from an external source rather than creating them itself. This promotes:

• Separation of concerns
• Code reuse and testability
• Flexibility in switching implementations

Both projects here use the same abstraction: IMessageSender, with two implementations:

• EmailSender
• SmsSender

🚀 How to Run

You can run any example individually.

📌 Prerequisites

.NET 9 SDK

▶️ Run ConsoleAppDI

cd ConsoleAppDI
dotnet run

You will see output like:

Email sent: Hello Dependency Injection!

To switch to SmsSender, edit the DI registration line in Program.cs:

services.AddTransient<IMessageSender, SmsSender>();

▶️ Run WebApiDI

cd WebApiDI
dotnet run

Once the API is running, you can send a POST request to:

POST https://localhost:5001/api/notification
Content-Type: application/json

"Hello from Web API!"

Expected console output:

Email sent: Hello from Web API!

To use SmsSender, change the registration in Program.cs:

builder.Services.AddTransient<IMessageSender, SmsSender>();

📂 Core Concepts Demonstrated

Constructor Injection

Interface-based abstraction (IMessageSender)

Manual vs Built-in DI container

Loose coupling