Disable a date in datetimepicker

List<datetime> bold = new List<datetime>();
for (int i = 0; i < 3; i++)
    bold.Add(DateTime.Now.AddDays(i*3).Date);

monthCalendar1.BoldedDates = bold.ToArray();

List<datetime> selected = new List<datetime>();

private void monthCalendar1_DateSelected(object sender, DateRangeEventArgs e)
{
    for   (DateTime dt = monthCalendar1.SelectionStart.Date; 
                    dt.Date <= monthCalendar1.SelectionEnd.Date; 
                    dt = dt.AddDays(1))
    {
        if (!monthCalendar1.BoldedDates.Contains(dt)
        && !selected.Contains(dt)) selected.Add(dt.Date);
    }
}