Select Multiple Non-Sequential Dates...

protected void Calendar1_SelectionChanged(object sender, EventArgs e)
{
Calendar1.SelectedDates.Clear();
Calendar1.SelectedDates.Add(new DateTime(2010, 7, 10));
Calendar1.SelectedDates.Add(new DateTime(2010, 7, 22));
Calendar1.SelectedDates.Add(new DateTime(2010, 7, 28));
}