using System;

public class Control
{

    // These members are private and thus invisible
    // to derived class methods; we'll examine this
    // later in the chapter
    private int top;
    private int left;

    // Constructor takes two integers to
    // fix location on the console
    public Control(int top, int left)
    {
        this.top = top;
        this.left = left;
    }

    // Simulates drawing the window
    public void DrawControl()
    {
        Console.WriteLine("Drawing Control at {0}, {1}",
            top, left);
    }
}

// TextBox derives from Control
public class TextBox : Control
{
    private string mTextBoxContents;  // new member variable

    // Constructor adds a parameter
    public TextBox(
        int top,
        int left,
        string theContents) :
        base(top, left) // call base constructor
    {
        mTextBoxContents = theContents;
    }


    // A new version (note keyword) because in the
    // derived method we change the behavior
    public new void DrawControl()
    {
        base.DrawControl();  // invoke the base method
        Console.WriteLine
            ("Writing string to the textbox: {0}", mTextBoxContents);
    }
}

public class Tester
{
    public static void Main()
    {
        // Create a base instance
        Control contr = new Control(5, 10);
        contr.DrawControl();

        // Create a derived instance
        TextBox txt = new TextBox(20, 30, "Hello world");
        txt.DrawControl();

        Console.ReadLine();
    }
}