dotnet/wpf · error · InvalidOperationException

Storyboard_TargetPropertyRequired

Storyboard_TargetPropertyRequired

Error message

SR.Format(SR.Storyboard_TargetPropertyRequired, currentTimeline.GetType().ToString())

What it means

ClockTreeWalkRecursive resolved a target object for a timeline but found no property path: Storyboard.TargetProperty was not set. An animation must know which property to animate, so Storyboard.Begin throws an InvalidOperationException identifying the timeline's type.

Solutions

Add Storyboard.TargetProperty="PropertyName" to the timeline (e.g. Opacity or (Canvas.Left)).
In code, call Storyboard.SetTargetProperty(animation, new PropertyPath("Opacity")).
Verify the property exists on the target type and use parenthesis syntax for attached/complex paths.

Example fix

// before
var anim = new DoubleAnimation(0, 1, TimeSpan.FromSeconds(1));
Storyboard.SetTargetName(anim, "MyPanel");
sb.Children.Add(anim); // no target property

// after
var anim = new DoubleAnimation(0, 1, TimeSpan.FromSeconds(1));
Storyboard.SetTargetName(anim, "MyPanel");
Storyboard.SetTargetProperty(anim, new PropertyPath("Opacity"));
sb.Children.Add(anim);

Defensive patterns

Strategy: validation

Validate before calling

if (Storyboard.GetTargetProperty(anim) == null)
    throw new InvalidOperationException("Timeline missing Storyboard.TargetProperty");

Type guard

bool HasTargetProperty(Timeline t) => Storyboard.GetTargetProperty(t) != null;

Try / catch

try { sb.Begin(fe); }
catch (InvalidOperationException ex) when (ex.Message.Contains(nameof(DoubleAnimation))) {
    // fix: add Storyboard.TargetProperty
}

Prevention

Set TargetProperty when creating each animation, before adding to the Storyboard.
In code, always pair SetTargetName with SetTargetProperty.
Watch for XAML attribute typos (TargetProperty vs Property).

When it happens

Trigger: A child animation (DoubleAnimation, ColorAnimation, etc.) lacks Storyboard.TargetProperty when the storyboard is begun, even if a target name/object was provided.

Common situations: Copy-pasting an animation and deleting the TargetProperty line; building animations in code with Storyboard.SetTargetName but forgetting Storyboard.SetTargetProperty; writing TargetProperty as 'Property' by mistake in XAML.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/61fc254e8df3767a. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Media/Animation/Storyboard.cs:453

                    // (Not a Storyboard, as used for "shared clocks" mode.)
                    targetObject = containingObject as FrameworkElement;
                    if(targetObject == null)
                    {
                        targetObject = containingObject as FrameworkContentElement;
                    }

                    if( targetObject == null )
                    {
                        // The containing object is not an FE or FCE.
                        throw new InvalidOperationException(SR.Format(SR.Storyboard_NoTarget, currentTimeline.GetType().ToString() ));
                    }
                }
            }

            // See if we have a property name to use.
            if( currentPropertyPath == null )
            {
                throw new InvalidOperationException(SR.Format(SR.Storyboard_TargetPropertyRequired, currentTimeline.GetType().ToString() ));
            }

            // A property name can be a straightforward property name (like "Angle")
            // but may be a more complex multi-step property path.  The two cases
            // are handled differently.
            using(currentPropertyPath.SetContext(targetObject))
            {
                if( currentPropertyPath.Length < 1 )
                {
                    throw new InvalidOperationException(SR.Storyboard_PropertyPathEmpty);
                }

                VerifyPathIsAnimatable(currentPropertyPath);

                if( currentPropertyPath.Length == 1 )
                {
                    // We have a simple single-step property.
                    targetProperty = currentPropertyPath.GetAccessor(0) as DependencyProperty;

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