C#

protected override void OnPaintBackground(PaintEventArgs e)
    {

    }
    private Bitmap _cachedBitmap;
    protected override void OnPaint(PaintEventArgs e)
    {
        using (Graphics g = e.Graphics)
        {
            if (!_isPainted)
            {
                _cachedBitmap = new Bitmap(ClientRectangle.Width, ClientRectangle.Height);
                InitilizeBitmap(g);
                _isPainted = true;
            }

            //Rectangle to show a particular portion of bitmap.
            Rectangle rec = new Rectangle(0, _bitmapLocation.Y, ClientRectangle.Width, ClientRectangle.Height);
            //using (Graphics gCached = Graphics.FromImage(_cachedBitmap))
            //{
            //   gCached.Clear(BackColor);
            //   gCached.DrawImage(_bmpControl, 0, 0, rec, GraphicsUnit.Pixel);
            //}

            //g.DrawImage(_cachedBitmap, 0, 0);
            g.DrawImage(_bmpControl, 0, 0, rec, GraphicsUnit.Pixel);
        }
    }