dotnet/reactive · error · ArgumentOutOfRangeException

throw new ArgumentOutOfRangeException(nameof(timeShift));

Error message

throw new ArgumentOutOfRangeException(nameof(timeShift));

What it means

Window(source, timeSpan, timeShift) uses timeShift to control how far apart successive windows start, so it must be non-negative. The public method throws ArgumentOutOfRangeException when timeShift is negative, since a negative shift would make windows start before their predecessors — an ill-defined schedule.

Solutions

Validate the shift duration is >= TimeSpan.Zero before the call, clamping if needed.
Fix the configuration or calculation producing the negative value.
Ensure timeSpan and timeShift arguments are not accidentally swapped.
Use a positive shift; for non-overlapping tumbling windows, set timeShift equal to timeSpan.

Example fix

// before
var windows = source.Window(TimeSpan.FromMinutes(1), TimeSpan.FromSeconds(-5));
// after
var shift = TimeSpan.FromSeconds(-5);
if (shift < TimeSpan.Zero) shift = TimeSpan.Zero;
var windows = source.Window(TimeSpan.FromMinutes(1), shift);

Defensive patterns

Strategy: validation

Validate before calling

if (timeShift < TimeSpan.Zero) throw new ArgumentOutOfRangeException(nameof(timeShift));

Try / catch

try
{
    var windows = source.Window(timeSpan, timeShift);
}
catch (ArgumentOutOfRangeException ex) when (ex.ParamName == "timeShift")
{
    // fall back to shift == timeSpan for tumbling windows
}

Prevention

Double-check argument order: (timeSpan, timeShift).
Clamp shift to zero when it may be negative.
For tumbling windows use timeShift == timeSpan; for sliding windows use 0 < timeShift < timeSpan.

When it happens

Trigger: Calling Window(source, TimeSpan.FromMinutes(1), TimeSpan.FromSeconds(-5)) — any negative TimeSpan supplied as the timeShift parameter.

Common situations: A configurable 'shift' or 'interval' setting that was entered as a negative number; sign errors when the shift is computed as a difference of two times; accidentally swapping the timeSpan and timeShift parameters so a validated negative lands in the shift slot.

Related errors

AI-assisted analysis of dotnet/reactive@94b5d5ab91 (2026-09-15). Data as JSON: /api/errors/4475c9cd9462eb8d. Report an issue: GitHub.

Appendix: source

Thrown at Rx.NET/Source/src/System.Reactive/Linq/Observable.Time.cs:2301

        /// However, this doesn't mean all windows will start at the beginning of the source sequence. This is a side-effect of the asynchrony introduced by the scheduler,
        /// where the action to create a new window may not execute immediately, despite the TimeSpan.Zero due time.
        /// </para>
        /// </remarks>
        public static IObservable<IObservable<TSource>> Window<TSource>(this IObservable<TSource> source, TimeSpan timeSpan, TimeSpan timeShift)
        {
            if (source == null)
            {
                throw new ArgumentNullException(nameof(source));
            }

            if (timeSpan < TimeSpan.Zero)
            {
                throw new ArgumentOutOfRangeException(nameof(timeSpan));
            }

            if (timeShift < TimeSpan.Zero)
            {
                throw new ArgumentOutOfRangeException(nameof(timeShift));
            }

            return s_impl.Window(source, timeSpan, timeShift);
        }

        /// <summary>
        /// Projects each element of an observable sequence into zero or more windows which are produced based on timing information, using the specified scheduler to run timers.
        /// </summary>
        /// <typeparam name="TSource">The type of the elements in the source sequence, and in the windows in the result sequence.</typeparam>
        /// <param name="source">Source sequence to produce windows over.</param>
        /// <param name="timeSpan">Length of each window.</param>
        /// <param name="timeShift">Interval between creation of consecutive windows.</param>
        /// <param name="scheduler">Scheduler to run windowing timers on.</param>
        /// <returns>An observable sequence of windows.</returns>
        /// <exception cref="ArgumentNullException"><paramref name="source"/> or <paramref name="scheduler"/> is null.</exception>
        /// <exception cref="ArgumentOutOfRangeException"><paramref name="timeSpan"/> or <paramref name="timeSpan"/> is less than TimeSpan.Zero.</exception>
        /// <remarks>
        /// <para>

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