C#

public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }
        Boolean bHaveMouse;
        Point ptOriginal = new Point();
        Point ptLast = new Point();

        // Called when the left mouse button is pressed. 
        public void MyMouseDown(Object sender, MouseEventArgs e)
        {
            // Make a note that we "have the mouse".
            bHaveMouse = true;
            // Store the "starting point" for this rubber-band rectangle.
            ptOriginal.X = e.X;
            ptOriginal.Y = e.Y;
            // Special value lets us know that no previous
            // rectangle needs to be erased.
            ptLast.X = -1;
            ptLast.Y = -1;
        }
        // Convert and normalize the points and draw the reversible frame.
        private void MyDrawReversibleRectangle(Point p1, Point p2)
        {
            Rectangle rc = new Rectangle();

            // Convert the points to screen coordinates.
            p1 = PointToScreen(p1);
            p2 = PointToScreen(p2);
            // Normalize the rectangle.
            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;
            }
            // Draw the reversible frame.
            ControlPaint.DrawReversibleFrame(rc,
                            Color.Black, FrameStyle.Thick);
           
        }
        // Called when the left mouse button is released.
        public void MyMouseUp(Object sender, MouseEventArgs e)
        {
            // Set internal flag to know we no longer "have the mouse".
            bHaveMouse = false;
             //If we have drawn previously, draw again in that spot
            // to remove the lines.
           // if (ptLast.X != -1)
           // {
            //    Point ptCurrent = new Point(e.X, e.Y);
             //   MyDrawReversibleRectangle(ptOriginal, ptLast);
           // }
            // Set flags to know that there is no "previous" line to reverse.
            ptLast.X = -1;
            ptLast.Y = -1;
           ptOriginal.X = -1;
            ptOriginal.Y = -1;
        }
        // Called when the mouse is moved.
        public void MyMouseMove(Object sender, MouseEventArgs e)
        {
            Point ptCurrent = new Point(e.X, e.Y);
            // If we "have the mouse", then we draw our lines.
            if (bHaveMouse)
            {
                // If we have drawn previously, draw again in
                // that spot to remove the lines.
                if (ptLast.X != -1)
                {
                  MyDrawReversibleRectangle(ptOriginal, ptLast);
                }
                // Update last point.
                ptLast = ptCurrent;
                // Draw new lines.
                MyDrawReversibleRectangle(ptOriginal, ptCurrent);
            }
        }
        // Set up delegates for mouse events.
        protected override void OnLoad(System.EventArgs e)
        {
            MouseDown += new MouseEventHandler(MyMouseDown);
            MouseUp += new MouseEventHandler(MyMouseUp);
            MouseMove += new MouseEventHandler(MyMouseMove);
            bHaveMouse = false;
        }

       

    }
}