CHOUFFAI.NET

private static int WM_NCPAINT = 0×0085;
private static int WM_ERASEBKGND = 0×0014;
private static int WM_PAINT = 0×000F;

[DllImport(“user32.dll”)]
static extern IntPtr GetDCEx(IntPtr hwnd, IntPtr hrgnclip, uint fdwOptions);
DllImport(“user32.dll”)]
static extern int ReleaseDC(IntPtr hwnd, IntPtr hDC);

protected override void WndProc(ref Message m)

{

    base.WndProc(ref m);

    if (m.Msg == WM_NCPAINT || m.Msg == WM_ERASEBKGND || m.Msg == WM_PAINT)

    {

        IntPtr hdc = GetDCEx(m.HWnd, (IntPtr)1, 1 | 0×0020);

        if (hdc != IntPtr.Zero)

        {

            Graphics graphics = Graphics.FromHdc(hdc);

            Color borderColor = Color.Blue;

            Rectangle rectangle = new Rectangle(0, 0, this.Width, this.Height);

            ControlPaint.DrawBorder(graphics, rectangle, borderColor, ButtonBorderStyle.Solid);

            m.Result = (IntPtr)1;

            ReleaseDC(m.HWnd, hdc);

        }

    }

}