I have a XamDataGrid where I use the XamDateTimeInput as EditTemplate for a TemplateField.
I don't use the default DateTimeField, because I think the Calendar of it is pretty ugly and wasn't able to change the it's Template to the one of the XamDateTimeInput.

I now have the problem, that I have a List of Dates that only shall be selectable, and have gaps between them. For example 14.08.2018 till 16.08.2018, 21.08.2018 and so on. Because of that MaxValue and MnValue aren't enough.
I have tried to use the ValueConstraint Enumeration, what threws an exception at the confirmation of the Value but I can still select the Date in the Calendar and so on.

                        <igDP:TemplateField.EditTemplate>
                            <DataTemplate>
                                <ig:XamDateTimeInput
                                    Value="{igEditors:TemplateEditorValueBinding}"
                                    >
                                    <ig:XamDateTimeInput.ValueConstraint>
                                        <ig:ValueConstraint Enumeration="{Binding Source={StaticResource enum}, Path=MyEnum}"/>
                                    </ig:XamDateTimeInput.ValueConstraint>
                                </ig:XamDateTimeInput>
                            </DataTemplate>
                        </igDP:TemplateField.EditTemplate>

Back with the XamDateTimeEditor I had the same problem, I tried to solve with the following code. But the loop takes extremely long.

private void XamDateTimeEditor_DropDownOpened(object sender, RoutedEventArgs e)
        {

            XamMonthCalendar xamMonthCalendar = Infragistics.Windows.Utilities.GetTemplateChild<XamMonthCalendar>((XamDateTimeEditor)sender);

            xamMonthCalendar.DisabledDaysOfWeek = Infragistics.Controls.DayOfWeekFlags.Sunday;
            xamMonthCalendar.MinDate = DateTime.Today;

            DataTable dt = Daten.GibNotAllowedDates(GlobaleVariablen.selGruppe);



            foreach (DataRow dr in dt.Rows)
            {
                Infragistics.Windows.Editors.CalendarDateRange calendarDateRange = new Infragistics.Windows.Editors.CalendarDateRange((DateTime)dr["Datum"]);
                xamMonthCalendar.DisabledDates.Add(calendarDateRange);

            }

        }