dotnet/wpf · error · ArgumentNullException

Int64KeyFrameCollection

Error message

Int64KeyFrameCollection[{0}]

What it means

The Int64KeyFrameCollection indexer setter throws ArgumentNullException with message 'Int64KeyFrameCollection[{index}]' when null is assigned at an index. Null key frames are invalid collection items.

Solutions

1. Null-check frames before indexer assignment.
2. Ensure frame factory/lookup code never returns null without handling.
3. Use KeyFrames.Add with validated instances.

Example fix

// before
keyFrames[i] = frames[i]; // frames[i] may be null
// after
if (frames[i] != null) keyFrames[i] = frames[i];

if (frame == null)
    throw new InvalidOperationException($"No key frame available for index {index}; refusing to insert null into Int64KeyFrameCollection.");

bool IsValidFrame(Int64KeyFrame f) => f != null;

try { keyFrames[index] = frame; }
catch (ArgumentNullException ex) when (ex.Message.Contains("Int64KeyFrameCollection[")) {
    // substitute a valid key frame or log and skip
}

When it happens

Trigger: Executing int64KeyFrames[index] = null; on an Int64KeyFrameCollection.

Common situations: Programmatic collection building with a null frame from a factory or lookup; data-driven frame generation failing silently.

Related errors

• Int32KeyFrameCollection
• PointKeyFrameCollection
• RectKeyFrameCollection
• ColorKeyFrameCollection
• DecimalKeyFrameCollection

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/0ec3bc786b13a251. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/Animation/Generated/Int64KeyFrameCollection.cs:466

            }
        }

        /// <summary>
        /// Gets or sets the Int64KeyFrame at a given index.
        /// </summary>
        public Int64KeyFrame this[int index]
        {
            get
            {
                ReadPreamble();

                return _keyFrames[index];
            }
            set
            {
                if (value == null)
                {
                    throw new ArgumentNullException(String.Format(CultureInfo.InvariantCulture, "Int64KeyFrameCollection[{0}]", index));
                }

                WritePreamble();

                if (value != _keyFrames[index])
                {
                    OnFreezablePropertyChanged(_keyFrames[index], value);
                    _keyFrames[index] = value;

                    Debug.Assert(_keyFrames[index] != null);

                    WritePostscript();
                }
            }
        }

        #endregion
    }

View on GitHub (pinned to 81131a70a4)