dotnet/wpf · error · InvalidOperationException

SR.Animation_NoTextChildren

Error message

SR.Animation_NoTextChildren

What it means

ColorAnimationUsingKeyFrames.AddText always throws InvalidOperationException (SR.Animation_NoTextChildren). Timelines have no text content model, so the IAddChild text path is intentionally unimplemented; the XML doc comment documents that text children are not supported.

Solutions

  1. Remove any text content inside the ColorAnimationUsingKeyFrames element in XAML
  2. Express values via key frame child elements instead of text
  3. If building content programmatically, use KeyFrames.Add rather than AddText
  4. Check for accidental characters/whitespace with non-trivial content between XAML tags

Example fix

// before (XAML)
<ColorAnimationUsingKeyFrames>Red</ColorAnimationUsingKeyFrames>
// after (XAML)
<ColorAnimationUsingKeyFrames>
  <DiscreteColorKeyFrame KeyTime="0:0:1" Value="Red" />
</ColorAnimationUsingKeyFrames>
Defensive patterns

Strategy: validation

Validate before calling

// check before building XAML content
bool hasTextContent = contentNode is text/whitespace-with-content; // reject before parse

Try / catch

try { addText(childText); }
catch (InvalidOperationException) { /* timelines never accept text; use key frames */ }

Prevention

When it happens

Trigger: Calling AddText(string) directly, or XAML/content parsing that attempts to place a literal text string inside a <ColorAnimationUsingKeyFrames> element.

Common situations: Stray whitespace-laden text or a literal value typed inside the animation element in XAML; programmatic code treating the animation as a text-bearing content element.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/cc2b43ea712948cc. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/Animation/Generated/ColorAnimationUsingKeyFrames.cs:277

        /// WritePreamble() or WritePostscript().  It also doesn't throw an
        /// ArgumentNullException if the childText parameter is null.  These tasks
        /// are performed by the interface implementation.  Therefore, it's OK
        /// for a derived class to override this method and call the base
        /// class implementation only if they determine that it's the right
        /// course of action.  The derived class can rely on KeyFrameAnimation's
        /// implementation of IAddChild.AddChild or implement their own
        /// following the Freezable pattern since that would be a public
        /// method.
        /// </remarks>
        /// <param name="childText">A string representing the child text that
        /// should be added.  If this is a KeyFrameAnimation an exception will be
        /// thrown.</param>
        /// <exception cref="InvalidOperationException">Timelines have no way
        /// of adding text.</exception>
        [EditorBrowsable(EditorBrowsableState.Advanced)]
        protected virtual void AddText(string childText)
        {
            throw new InvalidOperationException(SR.Animation_NoTextChildren);
        }

        #endregion

        #region ColorAnimationBase

        /// <summary>
        /// Calculates the value this animation believes should be the current value for the property.
        /// </summary>
        /// <param name="defaultOriginValue">
        /// This value is the suggested origin value provided to the animation
        /// to be used if the animation does not have its own concept of a
        /// start value. If this animation is the first in a composition chain
        /// this value will be the snapshot value if one is available or the
        /// base property value if it is not; otherise this value will be the 
        /// value returned by the previous animation in the chain with an 
        /// animationClock that is not Stopped.
        /// </param>

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