WinRTXamlToolkit.Controls.Calendar.OnDisplayDateStartChanged C# (CSharp) Method

        private static void OnDisplayDateStartChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            Calendar c = d as Calendar;
            Debug.Assert(c != null, "c should not be null!");

            if (!c.IsHandlerSuspended(Calendar.DisplayDateStartProperty))
            {
                DateTime? newValue = e.NewValue as DateTime?;

                if (newValue.HasValue)
                {
                    // DisplayDateStart coerces to the value of the
                    // SelectedDateMin if SelectedDateMin < DisplayDateStart
                    DateTime? selectedDateMin = SelectedDateMin(c);

                    if (selectedDateMin.HasValue && DateTime.Compare(selectedDateMin.Value, newValue.Value) < 0)
                    {
                        c.DisplayDateStart = selectedDateMin.Value;
                        return;
                    }

                    // if DisplayDateStart > DisplayDateEnd,
                    // DisplayDateEnd = DisplayDateStart
                    if (DateTime.Compare(newValue.Value, c.DisplayDateRangeEnd) > 0)
                    {
                        c.DisplayDateEnd = c.DisplayDateStart;
                    }

                    // If DisplayDate < DisplayDateStart,
                    // DisplayDate = DisplayDateStart
                    if (DateTimeHelper.CompareYearMonth(newValue.Value, c.DisplayDateInternal) > 0)
                    {
                        c.DisplayDate = newValue.Value;
                    }
                }
                c.UpdateMonths();
            }
        }