dotnet/wpf · error · InvalidOperationException

SR.Timing_RepeatBehaviorNotRepeatDuration

Error message

SR.Timing_RepeatBehaviorNotRepeatDuration

What it means

RepeatBehavior.Duration returns the stored TimeSpan only when the instance represents a repeat duration (HasDuration). Reading it on an IterationCount-based, Forever, or default RepeatBehavior throws InvalidOperationException with Timing_RepeatBehaviorNotRepeatDuration.

Solutions

  1. Guard with if (rb.HasDuration) before accessing rb.Duration.
  2. Handle the IterationCount and Forever cases explicitly instead of defaulting to Duration.
  3. If a duration is expected, construct with new RepeatBehavior(TimeSpan) and store the TimeSpan alongside instead of re-reading.

Example fix

// before
TimeSpan dur = repeatBehavior.Duration;
// after
TimeSpan dur = repeatBehavior.HasDuration ? repeatBehavior.Duration : TimeSpan.Zero;
Defensive patterns

Strategy: type-guard

Validate before calling

TimeSpan? dur = repeatBehavior.HasDuration ? repeatBehavior.Duration : (TimeSpan?)null;

Type guard

static bool HasRepeatDuration(RepeatBehavior rb) => rb.HasDuration;
static TimeSpan? SafeDuration(RepeatBehavior rb) => rb.HasDuration ? rb.Duration : (TimeSpan?)null;

Try / catch

TimeSpan dur;
try { dur = repeatBehavior.Duration; }
catch (InvalidOperationException) { dur = TimeSpan.Zero; }

Prevention

When it happens

Trigger: Reading rb.Duration when rb = new RepeatBehavior(3), rb == RepeatBehavior.Forever, or rb == default(RepeatBehavior). Only new RepeatBehavior(TimeSpan) instances support Duration.

Common situations: Generic animation inspection code that reads Duration for all repeat behaviors; copying a timeline's RepeatBehavior into a settings object assuming it is duration-based; XAML reload logic.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/e2ca03b0ffd48f78. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/Animation/RepeatBehavior.cs:126

            {
                if (!HasCount)
                    throw new InvalidOperationException(SR.Format(SR.Timing_RepeatBehaviorNotIterationCount, this));

                return _iterationCount;
            }
        }

        /// <summary>
        /// Returns the repeat duration specified by this RepeatBehavior.
        /// </summary>
        /// <value>A TimeSpan representing the repeat duration specified by this RepeatBehavior.</value>
        /// <exception cref="InvalidOperationException">Thrown if this RepeatBehavior does not represent a repeat duration.</exception>
        public TimeSpan Duration
        {
            get
            {
                if (!HasDuration)
                    throw new InvalidOperationException(SR.Format(SR.Timing_RepeatBehaviorNotRepeatDuration, this));

                return _repeatDuration;
            }
        }

        /// <summary>
        /// Creates and returns a <see cref="RepeatBehavior"/> that indicates that a <see cref="Timeline"/>
        /// should repeat its simple duration forever.
        /// </summary>
        /// <value>A <see cref="RepeatBehavior"/> that indicates that a <see cref="Timeline"/>
        /// should repeat its simple duration forever.</value>
        public static RepeatBehavior Forever
        {
            get
            {
                return new RepeatBehavior(RepeatBehaviorType.Forever);
            }
        }

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