using System;

​

public interface Tool 

{

    void MouseDown();

    void MouseUp();

}

​

public class SelectionTool: Tool 

{

    public void MouseDown() 

    {

        Console.WriteLine("Selection Icon");

    }

    public void MouseUp()

    {

        Console.WriteLine("Draw a dashed rectangle");

    }

}

public class BrushTool: Tool 

{

    public void MouseDown() 

    {

        Console.WriteLine("Brush Icon");

    }

    public void MouseUp()

    {

        Console.WriteLine("Draw a line");

    }

}

public class Canvas

{

    public Tool CurrentTool { get; set; }

    public void MouseDown()

    {

        CurrentTool.MouseDown();

    }

    public void MouseUp()

    {

        CurrentTool.MouseUp();

    }

}

​

public class Program

{

    public static void Main()

    {

        var canvas = new Canvas();

        canvas.CurrentTool = new SelectionTool();

        canvas.MouseDown();

        canvas.MouseUp();

        canvas.CurrentTool = new BrushTool();

        canvas.MouseDown();

        canvas.MouseUp();

    }

}