C#

class Program
{
    static List<Car> carList = new List<Car>();
    static Cars cars;

    static void Main(string[] args)
    {
        carList.Add(new Car("Black", "Volvo"));
        carList.Add(new Car("Blue", "Volvo"));
        carList.Add(new Car("Black", "Audi"));
        cars = new Cars(carList);

        string c = cars["Volvo"]   // IntelliSense  don't work

        foreach (Car car in cars["Volvo", "Blue"])
            Console.WriteLine(car.Color + " : "+ car.Model);
    }
}

class Cars
{
    List<Car> carList;

    public Cars(List<Car> carList)
    {
        this.carList = carList;
    }

    public Car this[string model]
    {
        get
        {
            foreach (Car car in carList)
            {
                if (car.Model == model)
                    return car;
            }
            return null;
        }
    }

    public List<Car> this[string model, string color]
    {
        get
        {
            List<Car> cars = new List<Car>();

            foreach (Car car in cars)
            {
                if (car.Model == model && car.Color == color)
                    cars.Add(car);
                    
            }
            return cars;
        }
    }
}

class Car
{
    string color;
    string model;

    public Car(string color, string model)
    {
        this.color = color;
        this.model = model;
    }

    public string Color
    {
        get { return color; }
        set { color = value; }
    }

    public string Model
    {
        get { return model; }
        set { model = value; }
    }
}

public List<Car> this[int amounth]
{
    get
    {
        List<Car> list = new List<Car>();

        for (int i = 0; i < amounth; i++)
            list.Add(carList[i]);

        return list;
    }
}

Bitmap b = new Bitmap(512, 300);
Graphics g = Graphics.FromImage(b);
TextureBrush tb = new TextureBrush(Image.FromFile(@"C:\dsfsdf.png"));
g.FillRectangle(tb, 80, 0, 512 - 80, 300);
tb.Dispose();
g.Dispose();
pictureBox1.Image = b;

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

namespace Inheritance_practice
{
    class Person
    {
        protect string name;
        protect string family;
        protect int age;

        public string _name
        {
            get { return name; }
            set { name = value; }
        }

        public string _family
        {
            get { return family; }
            set { family = value; }
        }

        public int _age
        {
            get { return age; }
            set {
                    age = value;
                    if (value > 100)
                     {
                        throw new ArgumentException(string.Format("Error.... !"));
                      }
                }
        }

        public Person(string Name, string Family, int Age)
        {
            this.name = Name;
            this.family = Family;
            this.age = Age;

        }
        public Person()
        {
        }

        //public override string ToString()
        //{
        //    return string.Format("Name: {0}\nSurname: {1}\nAge: {2}",name, family, age);
        //}
        
        }

    }

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

namespace Inheritance_practice
{
    class Student:Person
    {
        private string id;
        public string _id
        {
            get { return id; }
            set { id = value;}
        }
        public Student(string Name, string Family, int Age, string ID)
            : base(Name, Family, Age)
        {
            this.id = ID;
        }
        public Student()
        {
        }



        public override string ToString()
        {
            return base.string.Format(name,family,age)+string.Format("\nID:{0}", id);
        }
    }
}

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

namespace Inheritance_practice
{
    class Program
    {
        static void Main(string[] args)
        {
            Person p = new Person("Allen","Wilson",28);
            Student s = new Student();
            s._id = "30069802";



            Console.WriteLine(p);
            Console.WriteLine(s);
            Console.ReadKey();
        }
    }
}

class Program
{
    static void Main(string[] args)
    {
        try
        {
            Demo demo = new Demo();
            Timer timer1 = new Timer();
            timer1.Interval = 3000;
            timer1.Elapsed += new ElapsedEventHandler(demo.Run);
            timer1.Enabled = true;
        }
        catch (Exception e)
        {
            //I want this to catch the IllTellMyDadThreadException exception
            Console.WriteLine("You should write an exception handler");
        }
        Console.ReadKey();
    }
}

class Demo
{
    public void Run(object source, ElapsedEventArgs e)
    {
        try
        {
            System.Threading.Thread.Sleep(2000);
            DoSomething();
            System.Threading.Thread.Sleep(2000);
        }
        catch (Exception e)
        {
            throw new IllTellMyDadThreadException(e);
        }
    }
    private void DoSomething()
    {
        throw new Exception("aaaugh");
    }
}

class Program
{
    static void Main(string[] args)
    {
        Base one = new SubClass1();
        Base two = new SubClass2();
        Timer timer1 = new Timer();
        Timer timer2 = new Timer();
        timer1.Interval = 3000;
        timer1.Elapsed += new ElapsedEventHandler(one.Run);
        timer1.Enabled = true;
        timer2.Interval = 5000;
        timer2.Elapsed += new ElapsedEventHandler(two.Run);
        timer2.Enabled = true;System.Threading.Thread.Sleep(20000);
        Console.ReadKey();//allows the program to stay alive whilst the threads continue
    }
}
abstract class Base
{
    private volatile static bool sync = false;
    private static object syncroot = string.Empty;
    public void Run(object source, ElapsedEventArgs e)
    {
        if (sync) return;
        lock (syncroot)
        {
            if (sync) return;
            sync = true;
        }
        RunSubClassCode();
        sync = false;
    }
    protected abstract void RunSubClassCode();
}
class SubClass1: Base
{
    protected override void RunSubClassCode()
    {
        Console.WriteLine("1a");
        System.Threading.Thread.Sleep(2000);
        Console.WriteLine("1b");
    }
}
class SubClass2 : Base
{
    protected override void RunSubClassCode()
    {
        Console.WriteLine("2a");
        System.Threading.Thread.Sleep(2000);
        Console.WriteLine("2b");
    }
}