1.2 Basics: object orientation, C#

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//1.2 Basics: object orientation

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            //C# is object oriented. Object is an instance of a class. A class is user defined type.
            //When facing a  problem it's convinient to introduce some kind of entities that represent problem's domain entities.
            //These entities are described by classes.
            
            //So below we've described a Car entity and a Wheel one.
            //A class, or user defined type, can have data (like list of wheels) and methods that are supposed to process this data (like HowManyWheels method).
            //Classes are nice way of encapsulating data and logic.
            
            //Objects are instances of classes, they are created with keyword new and are kept in memory
            Car car = new Car();
            Car another_car = new Car();
            
            //Unlike primitive types, user defined types are passed by reference
            //I.e. when we pass object to a function, we pass its adress and not a copy
            Console.WriteLine(car.HowManyWheels());
            MutateCar(car);
            Console.WriteLine(car.HowManyWheels());
            
            //Created instance of types, or objects, will stay in memory for as long as someone keeps a reference to it
            //When object is not referenced anymore it will at some point be destroyed automatically
        }
        
        public static void MutateCar(Car car)
        {
            car.wheels = new List<Wheel>();
        }
    }
    
    public class Car
    {
        public List<Wheel> wheels = new List<Wheel> {new Wheel() {WheelType = 1}, new Wheel() {WheelType = 1},}; //this is just initialization of a list wheels with two wheels
        public int HowManyWheels()
        {
            return wheels.Count();
        }
    }
    
    public class Wheel
    {
        public int WheelType { get; set; }
    }
}

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Compilation time: 0.16 sec, absolute running time: 0.09 sec, cpu time: 0.09 sec, average memory usage: 16 Mb, average nr of threads: 4