Flat Style Dropdown Menu Not Drawing Correctly In Windows XP

[Dutchcoffee]

I'm having issues with drawing a flat style dropdown menu in XP. Below is the user control element code I'm using:

    public class FlattenCombo : ComboBox
    {
        private Brush BorderBrush = new SolidBrush(SystemColors.WindowFrame);
        private Brush ArrowBrush = new SolidBrush(SystemColors.ControlText);
        private Brush DropButtonBrush = new SolidBrush(SystemColors.Control);
        public Color HighlightColor { get; set; }
    
        private Color _ButtonColor = SystemColors.Control;
        public Color ButtonColor
        {
            get { return _ButtonColor; }
            set
            {
                _ButtonColor = value;
                DropButtonBrush = new SolidBrush(this.ButtonColor);
                this.Invalidate();
            }
        }
    
        private Color _borderColor = Color.Black;
        private ButtonBorderStyle _borderStyle = ButtonBorderStyle.Solid;
        //private static int WM_PAINT = 0x000F;
    
        [Category("Appearance")]
        public Color BorderColor
        {
            get { return _borderColor; }
            set
            {
                _borderColor = value;
                this.Invalidate(); // causes control to be redrawn
            }
        }
    
        [Category("Appearance")]
        public ButtonBorderStyle BorderStyle
        {
            get { return _borderStyle; }
            set
            {
                _borderStyle = value;
                this.Invalidate();
            }
        }
    
        protected override void WndProc(ref Message m)
        {
            base.WndProc(ref m);
    
            switch (m.Msg)
            {
                case 0xf:
                    //Paint the background. Only the borders will show up because the edit box will be overlayed
                    Graphics g = this.CreateGraphics();
                    Rectangle bounds = new Rectangle(0, 0, Width, Height);
                    ControlPaint.DrawBorder(g, bounds, _borderColor, _borderStyle);
    
                    //Draw the background of the dropdown button
                    Rectangle rect = new Rectangle(this.Width - 18, 0, 18, this.Height);
                    g.FillRectangle(DropButtonBrush, rect);
    
                    //Create the path for the arrow
                    System.Drawing.Drawing2D.GraphicsPath pth = new System.Drawing.Drawing2D.GraphicsPath();
                    PointF TopLeft = new PointF(this.Width - 13, (this.Height - 5) / 2);
                    PointF TopRight = new PointF(this.Width - 6, (this.Height - 5) / 2);
                    PointF Bottom = new PointF(this.Width - 9, (this.Height + 2) / 2);
                    pth.AddLine(TopLeft, TopRight);
                    pth.AddLine(TopRight, Bottom);
    
                    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
    
                    //Determine the arrow's color.
                    if (this.DroppedDown)
                        ArrowBrush = new SolidBrush(SystemColors.HighlightText);
                    else
                        ArrowBrush = new SolidBrush(SystemColors.ControlText);
    
                    //Draw the arrow
                    g.FillPath(ArrowBrush, pth);
    
                    break;
            }
        }
    
        //Override mouse and focus events to draw
        //proper borders. Basically, set the color and Invalidate(),
        //In general, Invalidate causes a control to redraw itself.
        //#region "Mouse and focus Overrides"
        protected override void onmouseenter(System.EventArgs e)
        {
            base.onmouseenter(e);
            //BorderBrush = new SolidBrush(SystemColors.Highlight);
            //EnableDoubleBuffering();
            this.Invalidate();
        }
    
        protected override void onmouseleave(System.EventArgs e)
        {
            base.onmouseleave(e);
            /*if (this.Focused)
                return;*/
            BorderBrush = new SolidBrush(SystemColors.WindowFrame);
            //EnableDoubleBuffering();
            this.Invalidate();
        }
    
        protected override void OnLostFocus(System.EventArgs e)
        {
            base.OnLostFocus(e);
            //BorderBrush = new SolidBrush(SystemColors.Window);
            //EnableDoubleBuffering();
            this.Invalidate();
        }
    
        protected override void OnGotFocus(System.EventArgs e)
        {
            base.OnGotFocus(e);
            BorderBrush = new SolidBrush(SystemColors.WindowFrame);
            //EnableDoubleBuffering();
            this.Invalidate();
        }
    
        protected override void OnMouseHover(System.EventArgs e)
        {
            base.OnMouseHover(e);
            BorderBrush = new SolidBrush(SystemColors.WindowFrame);
            //EnableDoubleBuffering();
            this.Invalidate();
        }
        //#endregion
    }

The problem I am having is that in Windows XP, the border colors aren't rendering properly. Here is what it looks like:



And here is what it *should* look like (this is how it renders in Vista and greater):



I looked at this documentation about building a custom combobox and focused on the WM_CTLCOLORLISTBOX message; however, I am not sure if this is the proper message to use to paint the combobox...and if it is, how to properly use it to draw the combobox.

If someone can point me in the right direction, I'd appreciate it.