{"record":{"id":"c94a144d3d929a8e","repo":"dotnet/wpf","slug":"sr-animation-childmustbekeyframe-c94a14","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/Int16AnimationUsingKeyFrames.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            Int16KeyFrame keyFrame = child as Int16KeyFrame;\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/Int16AnimationUsingKeyFrames.cs#L209-L245","documentation":"Int16AnimationUsingKeyFrames.AddChild throws ArgumentException(SR.Animation_ChildMustBeKeyFrame) when a child that is not an Int16KeyFrame (or is null) is added. Only Int16KeyFrame-derived objects are valid children of this key-frame animation.","triggerScenarios":"IAddChild.AddChild called with a non-keyframe object — e.g. nesting an Int16Animation or other timeline inside <Int16AnimationUsingKeyFrames> in XAML, or a null child passed programmatically.","commonSituations":"XAML mistakes using wrong key-frame type (e.g. DoubleKeyFrame inside an Int16 key-frame animation); code calling AddChild directly with a null or wrong-typed child.","solutions":["Nest only Int16KeyFrame-derived elements (DiscreteInt16KeyFrame, LinearInt16KeyFrame, SplineInt16KeyFrame, EasingInt16KeyFrame)","Match key-frame types to the animation's value type","Use KeyFrames.Add in code rather than AddChild"],"exampleFix":"// before (XAML)\n<Int16AnimationUsingKeyFrames>\n  <LinearDoubleKeyFrame Value=\"10\" KeyTime=\"0:0:1\" />\n</Int16AnimationUsingKeyFrames>\n// after\n<Int16AnimationUsingKeyFrames>\n  <LinearInt16KeyFrame Value=\"10\" KeyTime=\"0:0:1\" />\n</Int16AnimationUsingKeyFrames>","handlingStrategy":"validation","validationCode":"if (child == null || child is not Int16KeyFrame) throw new ArgumentException(\"Child must be an Int16KeyFrame\", nameof(child));","typeGuard":"static bool IsValidKeyFrameChild(object child) => child is Int16KeyFrame;","tryCatchPattern":"try { anim.AddChild(o); } catch (ArgumentException ex) { /* wrong child type — use KeyFrames.Add */ }","preventionTips":["Nest only Int16KeyFrame-derived elements in Int16AnimationUsingKeyFrames","Verify XAML key-frame element types match the animation's value type","Use the typed KeyFrames.Add API in code instead of AddChild"],"tags":["wpf","animation","xaml","keyframes","invalid-child"],"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"}