Can you explain DIP with an example in C#?

Short answer: ❌ Without DIP (Tightly Coupled): public class FileLogger

Example code

{
public void Log(string message) => Console.WriteLine("File log: " + message); }
public class OrderService
{
private readonly FileLogger _logger = new FileLogger();
public void ProcessOrder()
{ // Logic _logger.Log("Order processed."); }
} OrderService is tightly coupled to FileLogger. ✅ With DIP (Loosely Coupled via Abstraction): public interface ILogger
{ void Log(string message); }
public class FileLogger : ILogger
{
public void Log(string message) => Console.WriteLine("File log: " + message); }
public class OrderService
{
private readonly ILogger _logger;
public OrderService(ILogger logger)
{
_logger = logger;
}
public void ProcessOrder()
{ // Logic _logger.Log("Order processed."); }
} Now OrderService depends on the abstraction (ILogger), not the concrete FileLogger. You can easily substitute with DatabaseLogger, ConsoleLogger, or a mock in tests.

Real-world example (ShopNest)

Open/Closed in ShopNest: add a new payment method by adding a class, not by editing a giant switch in CheckoutService.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.