Dependency Injection (DI) is a technique for achieving loose coupling and easier testing.
🤝 What is DI?
- Instead of creating dependencies (classes/services) yourself, you “inject” them (usually via constructor parameters).
🏗️ Example
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public interface IMessageSender
{
void Send(string message);
}
public class EmailSender : IMessageSender
{
public void Send(string message) => Console.WriteLine($"Email: {message}");
}
public class NotificationService
{
private readonly IMessageSender _sender;
public NotificationService(IMessageSender sender) => _sender = sender;
public void Notify(string message) => _sender.Send(message);
}
🛠️ Registering Services in .NET Core
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services.AddTransient<IMessageSender, EmailSender>();
services.AddTransient<NotificationService>();
- Now, the DI framework will create and inject dependencies automatically.
🧪 Testing
- Easily swap out real implementations for mocks/fakes in tests.
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