dotnet/wpf · error · ArgumentOutOfRangeException

SR.Calendar_UnSelectableDates

Error message

SR.Calendar_UnSelectableDates

What it means

InsertItem throws ArgumentOutOfRangeException (with message SR.Calendar_UnSelectableDates) when the inserted CalendarDateRange is invalid for blackout purposes — the range fails IsValid, meaning it overlaps dates that must remain selectable (e.g. dates before DisplayDateStart or after DisplayDateEnd, or an invalid range).

Solutions

1. Validate the range against DisplayDateStart/DisplayDateEnd before adding
2. Check CalendarBlackoutDatesCollection.IsValid(range) before inserting
3. Clamp the range to the calendar's display range

Example fix

// before
calendar.BlackoutDates.Add(new CalendarDateRange(minDate, maxDate));
// after
var range = new CalendarDateRange(minDate, maxDate);
if (calendar.BlackoutDates.IsValid(range))
    calendar.BlackoutDates.Add(range);

bool ok = range.Start >= calendar.DisplayDateStart && range.End <= calendar.DisplayDateEnd
          && calendar.BlackoutDates.IsValid(range);
if (ok) calendar.BlackoutDates.Add(range);

bool IsBlackoutable(Calendar c, CalendarDateRange r) => c.BlackoutDates.IsValid(r);

try
{
    calendar.BlackoutDates.Add(range);
}
catch (ArgumentOutOfRangeException)
{
    // clamp range to display bounds or skip
}

When it happens

Trigger: Adding a CalendarDateRange that lies outside the Calendar's valid display range or otherwise fails CalendarBlackoutDatesCollection.IsValid (e.g. blacking out the entire calendar such that no selectable dates remain).

Common situations: Blackout dates computed from external data exceeding DisplayDateStart/DisplayDateEnd; blacking out today's date or all days; typos in hardcoded year ranges.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• SR.Calendar_OnSelectedDateChanged_InvalidValue
• args
• args
• ArgumentOutOfRangeException(authenticationType)
• ArgumentOutOfRangeException

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/be10ac440aeed6b7. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/CalendarBlackoutDatesCollection.cs:190

        /// </summary>
        /// <param name="index"></param>
        /// <param name="item"></param>
        protected override void InsertItem(int index, CalendarDateRange item)
        {
            if (!IsValidThread())
            {
                throw new NotSupportedException(SR.CalendarCollection_MultiThreadedCollectionChangeNotSupported);
            }

            if (IsValid(item))
            {
                RegisterItem(item);
                base.InsertItem(index, item);
                _owner.UpdateCellItems();
            }
            else
            {
                throw new ArgumentOutOfRangeException(SR.Calendar_UnSelectableDates);
            }
        }

        /// <summary>
        /// The item in the specified index is removed from the collection.
        /// </summary>
        /// <param name="index"></param>
        protected override void RemoveItem(int index)
        {
            if (!IsValidThread())
            {
                throw new NotSupportedException(SR.CalendarCollection_MultiThreadedCollectionChangeNotSupported);
            }

            if (index >= 0 && index < this.Count)
            {
                UnRegisterItem(Items[index]);
            }

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