public class User
    {
        public ShoppingCart ShoppingCart { get; set; }
        public void AddItem(string name) {
            // User class must know how to create OrderItem
            var item = new OrderItem() { Name = name };

            // User class must know how to add item to shopping cart
            ShoppingCart.Items.Add(item);
            
        }
        public void CheckOut() {
            // User class must know logic behind cost and discount calculations:
            // check for discount
            // check shipping method
            // check promotions
            // calculate total cost of items 
        }
    }
    public class OrderItem
    {
        public int Id { get; set; }
        public string Name { get; set; }

    }
    public class ShoppingCart
    {
        public int Id { get; set; }
        public List<OrderItem> Items { get; set; }
       
    }

 public class User
    {
        public ShoppingCart ShoppingCart { get; set; }
        
    }
    public class OrderItem
    {
        public int Id { get; set; }
        public string Name { get; set; }

    }
    public class ShoppingCart
    {
        public int Id { get; set; }
        public List<OrderItem> Items { get; set; }
        public void AddItem(string name)
        {
            // ShoppingCart class know how to create OrderItem
            var item = new OrderItem() { Name = name };

            // ShoppingCart class already know how to add item 
            Items.Add(item);

        }
        public void CheckOut()
        {
            // ShoppingCart class know logic behind cost and discount calculations:
            // check for discount
            // check shipping method
            // check promotions
            // calculate total cost of items 
        }
    }

public class ShapeWithoutPolymorphism
    {
        public double X { get; set; }
        public double Y { get; set; }
        public double Z { get; set; }
        public double Area(string shapeType)
        {
            switch (shapeType)
            {
                case "square":
                    return X * Y;
                case "rectangle":
                    return X * Y;
                case "trapze":
                    return (X + Z) * Y / 2;
                default:
                    return 0;
            }
        }
    }

  public abstract class Shape
    {
        public double X { get; set; }
        public double Y { get; set; }
        public virtual double Area()
        {
            return X * Y;
        }
    }
    public class Rectangle : Shape
    {
        // No need to override
    }
    public class Square : Shape
    {
        // No need to override
    }
    public class Trapze : Shape
    {
        public double Z { get; set; }
        public override double Area()
        {
            return (X + Z) * Y / 2;

        }
    }

public class User
    {
        public int Id { get; set; }
        public string UserName { get; set; }
        public string Password { get; set; }
    }

    public class LibraryManagement
    {
        public User CurrentUser { get; set; }
        public void AddBookToLibrary(int bookId)
        {
            // check for CurrentUser authority:
            // not user's responsibility nor LibraryManagement
        }
        public void RearrangeBook(int bookId, int shelfId)
        {
            // check for CurrentUser authority
            // not user's responsibility nor LibraryManagement
        }
    }
    public class UserManagement
    {
        public User CurrentUser { get; set; }
        public void AddUser(string name)
        {
            // check for CurrentUser authority:
            // not user's responsibility nor UserManagement
        }
        public void ChangeUserRole(int userId, int roleId)
        {
            // check for CurrentUser authority
            // not user's responsibility nor UserManagement
        }
    }
    public class AuthorizationService
    {
        public bool IsAuthorized(int userId, int roleId)
        {
            // get user roles from data base
            // return true if user has the authority
        }
    }

public class TestController
{
    private readonly ILogger<TestController> _logger;
    public TestController(ILogger<TestController> logger)
    {
        _logger = logger;
    }

   [HttpGet("/")]
    public string Get()
    {
        _logger.LogInformation("hello world");
          return "Hello world!";
    }
}

CA1848: For improved performance, use the LoggerMessage delegates instead of calling LogInformation

public record Person (int Id, string Name);

var person = new Person(123, "Test");

_logger.LogInformation("hello to {Person}", person);

info: TestController[0]
hello world to Person { Id = 123, Name = Test }

_logger.LogInformation($"hello world to {person}"); // Using interpolation instead of structured logging

if (_logger.IsEnabled(LogLevel.Information))
{
   _logger.LogInformation("hello world to {Person}", person);
}

_logger.LogInformation("hello world to {Person} because {Reason}", person);

private static readonly Action<ILogger, Person, Exception?> _logHelloWorld =
    LoggerMessage.Define<Person>(
        logLevel: LogLevel.Information,
        eventId: 0,
        formatString: "hello world to {Person}");

[HttpGet("/")]
public string Get()
{
    var person = new Person(123, "Test");
    _logHelloWorld(_logger, person, null);
      return "Hello world!";
}

public partial class TestController
{
   [LoggerMessage(0, LogLevel.Information, "hello world to {Person}")]
   partial void LogHelloWorld(Person person);
}

[LoggerMessage(0, LogLevel.Information, "hello world to {Person} with a {Reason}")]
partial void LogHelloWorld(Person person);

[LoggerMessage(Message = "hello world to {Person}")]
partial void LogHelloWorld(LogLevel logLevel, Person person);