protected override void OnPaint(PaintEventArgs e)
{
int itemCount = Math.Max(myParent.Items.Count, 1);
Graphics g = e.Graphics;
int visibleCount = myParent.ClientSize.Height / myParent.GetItemHeight(0);
int topIndex = myParent.TopIndex;
int bottomIndex = Math.Min(topIndex + visibleCount, itemCount);
int maxScrollPos = Math.Max(itemCount - topIndex, 0);
int scrollHeight = Size.Height - 17 * 2;
int scrollBarTop = (int)Math.Ceiling((double)scrollHeight / (double)itemCount * (double)topIndex);
int scrollBarBottom = (int)Math.Ceiling((double)scrollHeight / (double)itemCount * (double)bottomIndex);
g.FillRectangle(new SolidBrush(frmMain.light), new Rectangle(0, 0, 17, 17));
g.FillRectangle(new SolidBrush(frmMain.light), new Rectangle(0, Size.Height - 17, 17, 17));
g.FillRectangle(new SolidBrush(frmMain.light), new Rectangle(0, 19 + scrollBarTop, 17, scrollBarBottom - scrollBarTop - 4));
StringFormat stringFormat = new StringFormat();
stringFormat.Alignment = StringAlignment.Center;
stringFormat.LineAlignment = StringAlignment.Center;
SolidBrush textCol = new SolidBrush(BackColor);
g.DrawString("▲", Font, textCol, new Rectangle(1, 1, 17, 17), stringFormat);
g.DrawString("▼", Font, textCol, new Rectangle(1, Size.Height - 16, 17, 17), stringFormat);
}