How to find the four coordinates and erase drawing of an rubberband rectangle in C#

using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Data;
 using System.Drawing;
 using System.Text;
 using System.Windows.Forms;

namespace rubberbandrectangle
{
public partial class Form1 : Form
{
    Boolean bHaveMouse;
    Point ptOriginal = new Point();
    Point ptLast = new Point();


    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_MouseDown(object sender, MouseEventArgs e)
    {
        bHaveMouse = true;
        ptOriginal.X = e.X;
        ptOriginal.Y = e.Y;
        ptLast.X = -1;
        ptLast.Y = -1;
    }

    private void MyDrawReversibleRectangle(Point p1, Point p2)
    {
        Rectangle rc = new Rectangle();

        p1 = PointToScreen(p1);
        p2 = PointToScreen(p2);
        if (p1.X < p2.X)
        {
            rc.X = p1.X;
            rc.Width = p2.X - p1.X;
        }
        else
        {
            rc.X = p2.X;
            rc.Width = p1.X - p2.X;
        }
        if (p1.Y < p2.Y)
        {
            rc.Y = p1.Y;
            rc.Height = p2.Y - p1.Y;
        }
        else
        {
            rc.Y = p2.Y;
            rc.Height = p1.Y - p2.Y;
        }
        ControlPaint.DrawReversibleFrame(rc,
                        Color.Red, FrameStyle.Dashed);
    }

    private void Form1_MouseUp(object sender, MouseEventArgs e)
    {
        bHaveMouse = false;
        if (ptLast.X != -1)
        {
            Point ptCurrent = new Point(e.X, e.Y);
            MyDrawReversibleRectangle(ptOriginal, ptLast);
        }
        ptLast.X = -1;
        ptLast.Y = -1;
        ptOriginal.X = -1;
        ptOriginal.Y = -1;
    }

    private void Form1_MouseMove(object sender, MouseEventArgs e)
    {
        Point ptCurrent = new Point(e.X, e.Y);
        if (bHaveMouse)
        {
            if (ptLast.X != -1)
            {
                MyDrawReversibleRectangle(ptOriginal, ptLast);
            }
            ptLast = ptCurrent;
                MyDrawReversibleRectangle(ptOriginal, ptCurrent);
        }
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        MouseDown += new MouseEventHandler(Form1_MouseDown);
        MouseUp += new MouseEventHandler(Form1_MouseUp);
        MouseMove += new MouseEventHandler(Form1_MouseMove);
        bHaveMouse = false;
    }





}
}