Drawing a Selection Rubber Band Like Explorer - Improved

I heard criticism about my first post on the topic: if a control was on the form, apart from the background drawing, the rubber rectangle would appear behind the control, not in front of it. Of course there are several ways to change this, I decided to implement one of them just for fun 😃 This is what things look like before and after my changes:

Here’s the complete code again, which will need the same changes as before if it is to be used in VS 2003 (see the comments on the first post for this).

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Drawing2D;

namespace SelectionRectTest {
  public class Form1 : Form {
    public Form1( ) {
      InitializeComponent( );
      BackColor = Color.White;
    }

    protected override void OnPaint(PaintEventArgs e) {
      if (selectionPanel == null) {
        e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;

        // Draw some stuff so the transparent selection becomes visible
        int height = ClientRectangle.Height;
        int heightTenth = height / 10;
        int width = ClientRectangle.Width;
        int widthTenth = width / 10;

        e.Graphics.DrawLines(Pens.Red, new Point[] {
          new Point(widthTenth, heightTenth * 3),
          new Point(widthTenth * 5, heightTenth),
          new Point(widthTenth * 8, heightTenth * 9),
          new Point(widthTenth, heightTenth * 3)
        });
        e.Graphics.DrawEllipse(Pens.Blue,
          widthTenth * 4,
          heightTenth * 3,
          widthTenth * 5,
          heightTenth * 4);
      }
    }

    protected override void OnResize(EventArgs e) {
      base.OnResize(e);
      Invalidate( );
    }

    Point mouseDownPos = Point.Empty;

    protected override void OnMouseDown(MouseEventArgs e) {
      base.OnMouseDown(e);

      if (e.Button == MouseButtons.Left)
        mouseDownPos = e.Location;

      Bitmap contentBitmap = new Bitmap(Bounds.Width, Bounds.Height);
      Rectangle targetRect = Bounds;
      targetRect.X = 0 ;
      targetRect.Y = 0;
      DrawToBitmap(contentBitmap, targetRect);

      Point originScreen = PointToScreen(new Point(0, 0));
      Rectangle usableRect = new Rectangle(
          new Point(originScreen.X - Bounds.X,
            originScreen.Y - Bounds.Y),
          ClientRectangle.Size);

      selectionPanel = new SelectionPanel(
        contentBitmap, usableRect, mouseDownPos);
      Controls.Add(selectionPanel);
      selectionPanel.BringToFront( );
    }

    SelectionPanel selectionPanel;

    protected override void OnMouseMove(MouseEventArgs e) {
      base.OnMouseMove(e);
      if (e.Button == MouseButtons.Left &&
        mouseDownPos != Point.Empty &&
        selectionPanel != null)
        selectionPanel.Invalidate( );
    }

    protected override void OnMouseUp(MouseEventArgs e) {
      base.OnMouseUp(e);
      mouseDownPos = Point.Empty;
      Controls.Remove(selectionPanel);
      selectionPanel = null;
    }

    private Button button1;

    private void InitializeComponent( ) {
      this.button1 = new System.Windows.Forms.Button( );
      this.SuspendLayout( );
      //
      // button1
      //
      this.button1.Location = new System.Drawing.Point(114, 108);
      this.button1.Name = "button1";
      this.button1.Size = new System.Drawing.Size(75, 33);
      this.button1.TabIndex = 0;
      this.button1.Text = "button1";
      //
      // Form1
      //
      this.ClientSize = new System.Drawing.Size(292, 266);
      this.Controls.Add(this.button1);
      this.Name = "Form1";
      this.ResumeLayout(false);
    }
  }

  public class SelectionPanel : Panel {
    public SelectionPanel(Bitmap backgroundBitmap,
      Rectangle usableRect, Point mouseDownPos) {
      DoubleBuffered = true;

      this.backgroundBitmap = backgroundBitmap;
      this.mouseDownPos = mouseDownPos;
      this.usableRect = usableRect;

      this.Size = usableRect.Size;
      this.Location = new Point(0, 0);

      selectionColor = Color.FromArgb(200, 0xE8, 0xED, 0xF5);
      selectionBrush = new SolidBrush(selectionColor);
      frameColor = Color.FromArgb(0x33, 0x5E, 0xA8);
      framePen = new Pen(frameColor);
    }

    Bitmap backgroundBitmap;
    Point mouseDownPos;
    Color selectionColor;
    Brush selectionBrush;
    Color frameColor;
    Pen framePen;
    Rectangle usableRect;

    protected override void OnPaint(PaintEventArgs e) {
      // copy the backgroundImage
      e.Graphics.DrawImage(backgroundBitmap,
        ClientRectangle, usableRect, GraphicsUnit.Pixel);

      // Now, if needed, draw the selection rectangle
      if (mouseDownPos != Point.Empty) {
        Point mousePos = PointToClient(MousePosition);
        Rectangle selectedRect = new Rectangle(
          Math.Min(mouseDownPos.X, mousePos.X),
          Math.Min(mouseDownPos.Y, mousePos.Y),
          Math.Abs(mousePos.X - mouseDownPos.X),
          Math.Abs(mousePos.Y - mouseDownPos.Y));
        e.Graphics.FillRectangle(selectionBrush, selectedRect);
        e.Graphics.DrawRectangle(framePen, selectedRect);
      }
    }
  }
}

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