Creational Patterns

public interface INotification
{
  void Send(string message);
}

public class EmailNotification : INotification
{
  public void Send(string message) { ... }
}

public class SmsNotification : INotification
{
  public void Send(string message) { ... }
}

enum NotificationType { Email, Sms }

public static class NotificationFactory
{
  public static INotification Create(NotificationType notificationType) =>
    notificationType switch {
      NotificationType.Email => new EmailNotification(),
      NotificationType.Sms => new SmsNotification(),
      _ => throw new ArgumentException("Unknown type")
    };
}