{"record":{"id":"62972c3fe36038a3","repo":"dotnet/wpf","slug":"sr-animation-childmustbekeyframe-62972c","errorCode":null,"errorMessage":"SR.Animation_ChildMustBeKeyFrame","messagePattern":"SR\\.Animation_ChildMustBeKeyFrame","errorType":"exception","errorClass":"ArgumentException","httpStatus":null,"severity":"error","filePath":"src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/Animation/Generated/Int64AnimationUsingKeyFrames.cs","lineNumber":227,"sourceCode":"            WritePostscript();\n        }\n\n        /// <summary>\n        /// Implemented to allow KeyFrames to be direct children\n        /// of KeyFrameAnimations in markup.\n        /// </summary>\n        [EditorBrowsable(EditorBrowsableState.Advanced)]\n        protected virtual void AddChild(object child)\n        {\n            Int64KeyFrame keyFrame = child as Int64KeyFrame;\n\n            if (keyFrame != null)\n            {\n                KeyFrames.Add(keyFrame);\n            }\n            else\n            {        \n                throw new ArgumentException(SR.Animation_ChildMustBeKeyFrame, nameof(child));\n            }\n        }\n\n        /// <summary>\n        /// Adds a text string as a child of this KeyFrameAnimation.\n        /// </summary>\n        /// <param name=\"childText\">\n        /// The text to add.\n        /// </param>\n        /// <remarks>\n        /// A KeyFrameAnimation does not accept text as a child, so this method will\n        /// raise an InvalididOperationException unless a derived class has\n        /// overridden the behavior to add text.\n        /// </remarks>\n        /// <exception cref=\"ArgumentNullException\">The childText parameter is\n        /// null.</exception>\n        void IAddChild.AddText(string childText)\n        {","sourceCodeStart":209,"sourceCodeEnd":245,"githubUrl":"https://github.com/dotnet/wpf/blob/81131a70a4c573cd62748a5c36908fc4d662daa9/src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/Animation/Generated/Int64AnimationUsingKeyFrames.cs#L209-L245","documentation":"Int64AnimationUsingKeyFrames.AddChild throws ArgumentException when the supplied child is not a (non-null) Int64KeyFrame. Only key frames of the matching integer type are valid children of this timeline.","triggerScenarios":"XAML declaring a child that is not an Int64KeyFrame inside <Int64AnimationUsingKeyFrames>, or programmatic AddChild with an incompatible object.","commonSituations":"Mixing key frame types across animations (e.g. Int32KeyFrame inside an Int64 animation); XAML paste errors.","solutions":["Use Int64KeyFrame-derived children (DiscreteInt64KeyFrame, LinearInt64KeyFrame, etc.).","Correct the XAML child element type to match the animation.","Prefer KeyFrames.Add with a typed key frame in code."],"exampleFix":"// before\n<Int64AnimationUsingKeyFrames>\n  <LinearInt32KeyFrame KeyTime=\"0:0:1\" Value=\"100\" />\n</Int64AnimationUsingKeyFrames>\n// after\n<Int64AnimationUsingKeyFrames>\n  <LinearInt64KeyFrame KeyTime=\"0:0:1\" Value=\"100\" />\n</Int64AnimationUsingKeyFrames>","handlingStrategy":"validation","validationCode":"if (child is not Int64KeyFrame)\n    throw new ArgumentException(\"Children of Int64AnimationUsingKeyFrames must be Int64KeyFrame instances\", nameof(child));","typeGuard":"bool IsInt64KeyFrame(object o) => o is Int64KeyFrame;","tryCatchPattern":"try { animation.AddChild(child); }\ncatch (ArgumentException ex) when (ex.ParamName == \"child\") {\n    // swap in the correctly typed Int64KeyFrame\n}","preventionTips":["Match key frame child types to the animation value type (Int64 vs Int32)","Check markup after refactoring animation value types","Use KeyFrames.Add in code for compile-time type safety"],"tags":["wpf","animation","xaml","type-mismatch"],"backgroundTag":"invalid-argument-value","analyzedSha":"81131a70a4c573cd62748a5c36908fc4d662daa9","analyzedAt":"2026-09-14T10:12:48.479Z","contentChangedAt":"2026-09-14T10:12:48.479Z","schemaVersion":2},"datasetVersion":"2026-09-22T01:17:13.364Z"}