What approaches and techniques ensure adherence to the dependency inversion principle in system design?

The Dependency Inversion Principle in system design is achieved through the following approaches and techniques:

• Using abstractions instead of concrete implementations. Classes should depend on interfaces or abstract classes, not on concrete classes.
• Dependency Injection. Dependencies are passed into a class from outside (via constructor, properties, or methods), rather than being created inside it.
• Inversion of Control (IoC). Control over object creation and binding is delegated to an external container or framework.

Example in C# with dependency injection:

public interface ILogger
{
    void Log(string message);
}

public class ConsoleLogger : ILogger
{
    public void Log(string message) => Console.WriteLine(message);
}

public class UserService
{
    private readonly ILogger _logger;

    public UserService(ILogger logger)
    {
        _logger = logger; // dependency is passed from outside
    }

    public void CreateUser(string name)
    {
        // user creation logic
        _logger.Log($"User {name} created.");
    }
}

This approach facilitates testing, extensibility, and code maintenance.