protected virtual void OnVisibilityChanged(CalendarEventArgs e)
 {
     if (VisibilityChangedEvent != null)
     {
         VisibilityChangedEvent(this, e);
     }
 }
        protected void Calendar_SelectDate(object sender, EventArgs e)
        {
            DOBTextBox.Text  = Calendar.SelectedDate.ToShortDateString();
            Calendar.Visible = false;
            CalendarEventArgs calendarEventArgs = new CalendarEventArgs(false);

            OnVisibilityChanged(calendarEventArgs);
        }
 protected void CalendarButton_Click(object sender, EventArgs e)
 {
     if (Calendar.Visible)
     {
         Calendar.Visible = false;
         CalendarEventArgs calendarEventArgs = new CalendarEventArgs(false);
         OnVisibilityChanged(calendarEventArgs);
     }
     else
     {
         Calendar.Visible = true;
         CalendarEventArgs calendarEventArgs = new CalendarEventArgs(true);
         OnVisibilityChanged(calendarEventArgs);
     }
 }