dotnet/wpf · error · ArgumentException

Invalid ISF data

Error message

Invalid ISF data

What it means

LoadStrokeIds decodes the stroke-ID count from the raw ISF stream and throws ArgumentException("Invalid ISF data") when the encoded count occupies more bytes than remain (cb > cbTotal). This is a structural validation: the ID-count field cannot exceed the remaining payload, so the data is malformed.

Solutions

1. Verify the ISF payload is complete and uncorrupted before loading
2. Re-save the ink data from the original application
3. Catch ArgumentException around StrokeCollection construction
4. Check that any ISF-in-GIF extraction logic reads the correct byte range

Example fix

// before
var strokes = new StrokeCollection(gifStream);
// after
try { var strokes = new StrokeCollection(gifStream); }
catch (ArgumentException ex) { if (ex.Message.Contains("Invalid ISF")) { /* handle corrupt ink */ } }

// verify the stream is a complete ISF/GIF payload before construction
bool HasValidHeader(Stream s) {
  var b = new byte[8]; int n = s.Read(b,0,8); s.Position = 0;
  return n == 8 && (b[0]==0x89 && b[1]==(byte)'P' || b[0]==(byte)'G');
}

try { strokes = new StrokeCollection(stream); }
catch (ArgumentException ex) when (ex.ParamName == "stream") { HandleCorruptInk(); }

When it happens

Trigger: DecodeRawISF on a stream whose stroke-ID block claims a byte length larger than the remaining data, typically via DecodeRawISF/DecodeISF triggered by new StrokeCollection(Stream).

Common situations: Truncated or corrupted ISF payloads, offsets computed incorrectly when embedding ISF in GIF, ink data produced by incompatible writers.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• invalid huffman encoded data
• Invalid size specified
• InvalidDataInISF
• InvalidDrawingAttributesWidth
• Buffer range is smaller than expected expected size

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/1ddd5f88354a2422. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/MS/internal/Ink/InkSerializedFormat/InkSerializer.cs:208

        #region Private Methods

        /// <summary>
        /// Loads the strokeIds from the stream, we need to do this to decrement the count of bytes
        /// </summary>
        internal uint LoadStrokeIds(Stream isfStream, uint cbSize)
        {
            if (0 == cbSize)
                return 0;

            uint cb;
            uint cbTotal = cbSize;

            // First decode the no of ids
            uint count;

            cb = SerializationHelper.Decode(isfStream, out count);
            if (cb > cbTotal)
                throw new ArgumentException(ISFDebugMessage("Invalid ISF data"), nameof(isfStream));

            cbTotal -= cb;
            if (0 == count)
                return (cbSize - cbTotal);

            cb = cbTotal;

            byte[] inputdata = new byte[cb];

            // read the stream
            uint bytesRead = StrokeCollectionSerializer.ReliableRead(isfStream, inputdata, cb);
            if (cb != bytesRead)
            {
                throw new ArgumentException(StrokeCollectionSerializer.ISFDebugMessage("Read different size from stream then expected"), nameof(isfStream));
            }
            cbTotal -= cb;

            if (0 != cbTotal)

View on GitHub (pinned to 81131a70a4)