dotnet/wpf · error · InvalidOperationException

SR.IAnimatable_CantAnimateSealedDO (formatted with dp and…

Error message

SR.IAnimatable_CantAnimateSealedDO (formatted with dp and this.GetType())

What it means

UIElement.BeginAnimation throws InvalidOperationException(SR.IAnimatable_CantAnimateSealedDO, formatted with the DP and this.GetType()) when the element IsSealed. Animation mutates the dependency-object's state, which is forbidden on sealed/frozen DependencyObjects, so the library throws before starting the animation.

Solutions

Clone the freezable (Clone()/CloneCurrentValue()) so an unfrozen instance can be animated, then assign it back.
Avoid Freeze() on objects that will be animated.
Animate via the owning element instead (e.g. animate element.RenderTransform's properties on an unfrozen transform).

Example fix

// before
translateTransform.Freeze();
translateTransform.BeginAnimation(TranslateTransform.XProperty, anim);
// after
var t = translateTransform.Clone(); // keep unfrozen
t.BeginAnimation(TranslateTransform.XProperty, anim);
element.RenderTransform = t;

Defensive patterns

Strategy: type-guard

Validate before calling

if (target is Freezable fr && fr.IsFrozen) { target = fr.Clone(); } // animate unfrozen instance

Type guard

bool CanBeginAnimation(DependencyObject o) => o is not Freezable f || !f.IsFrozen;

Try / catch

try { target.BeginAnimation(dp, anim, hb); }
catch (InvalidOperationException) { var clone = ((Freezable)target).Clone(); clone.BeginAnimation(dp, anim, hb); owner = clone; }

Prevention

Skip Freeze() on objects that will be animated.
Check IsFrozen before animation calls.
Animate parent elements rather than frozen shared resources.

When it happens

Trigger: Calling BeginAnimation on a frozen Freezable (Brush, Pen, Geometry, Transform) or otherwise sealed DependencyObject; animating a shared frozen resource instance.

Common situations: Styles/resources that froze a brush, then code tries to animate it; calling Freeze() earlier in the object lifetime; animating a frozen Transform used in a RenderTransform that was frozen for performance.

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/1242e5660da1d15e. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Generated/UIElement.cs:152

            if (!AnimationStorage.IsPropertyAnimatable(this, dp))
            {
                throw new ArgumentException(SR.Format(SR.Animation_DependencyPropertyIsNotAnimatable, dp.Name, this.GetType()), nameof(dp));
            }

            if (animation != null
                && !AnimationStorage.IsAnimationValid(dp, animation))
            {
                throw new ArgumentException(SR.Format(SR.Animation_AnimationTimelineTypeMismatch, animation.GetType(), dp.Name, dp.PropertyType), nameof(animation));
            }

            if (!HandoffBehaviorEnum.IsDefined(handoffBehavior))
            {
                throw new ArgumentException(SR.Animation_UnrecognizedHandoffBehavior);
            }

            if (IsSealed)
            {
                throw new InvalidOperationException(SR.Format(SR.IAnimatable_CantAnimateSealedDO, dp, this.GetType()));
            }

            AnimationStorage.BeginAnimation(this, dp, animation, handoffBehavior);
        }

        /// <summary>
        /// Returns true if any properties on this DependencyObject have a
        /// persistent animation or the object has one or more clocks associated
        /// with any of its properties.
        /// </summary>
        public bool HasAnimatedProperties
        {
            get
            {
                VerifyAccess();

                return IAnimatable_HasAnimatedProperties;
            }

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