using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        List<Control> listOfControls = new List<Control>();

        listOfControls.Add(new Button(0, 100, "click"));

        listOfControls.Add(new ListBox(10, 20, new List<string>()));

        foreach (Control control in listOfControls)

        {

            control.Draw();

        }

    }

}

​

public abstract class Control

{

    protected int xPos;

    protected int yPos;

    public Control(int xPosition, int yPosition)

    {

        xPos = xPosition;

        yPos = yPosition;

    }

​

    public virtual void Clear()

    {

        Console.WriteLine("Clearing control");

    }

​

    public abstract void Draw();

}

​

public class Button : Control

{

    private string text;

    public Button(int xPosition, int yPosition, string buttonText): base (xPosition, yPosition)

    {

        text = buttonText;

    }

​

    public override void Draw()

    {

        Console.WriteLine("Drawing button...");

    }

}

​

public class ListBox : Control

{

    private List<string> list = new List<string>();

    public ListBox(int xPosition, int yPosition, List<string> contents): base (xPosition, yPosition)

    {

        list = contents;

    }

​

    public override void Draw()

    {

        Console.WriteLine("Drawing listbox....");

    }

}