icsharpcode/ILSpy · error · InvalidDataException

BAML defer record points at an offset that is not a record…

Error message

BAML defer record points at an offset that is not a record boundary.

What it means

Thrown during the second pass of BamlReader.ReadDocument, when resolving IBamlDeferRecord entries (e.g. DeferableContentStart). A defer record references a stream offset that is not present in the map of record start positions, so the deferred content cannot be linked. InvalidDataException signals corrupt or internally inconsistent BAML.

Solutions

1. Re-extract the BAML resource from a known-good assembly.
2. Treat the resource as corrupt and skip it.
3. Report the failing offset for diagnosis.

try {
    var doc = BamlReader.ReadDocument(stream, token);
} catch (InvalidDataException ex) when (ex.Message.Contains("record boundary")) {
    // deferable content references a bad offset; BAML is corrupt
}

When it happens

Trigger: A DeferableContentStart record (or similar) points at an offset that is mid-record or beyond the stream, so recs.TryGetValue(offset) fails. Caused by corrupted/truncated BAML or a malformed deferable-content section.

Common situations: Truncated BAML resource; bit-flipped offset field; BAML assembled by a broken tool.

Related errors

• Invalid BAML signature length.
• {ser}
• {type}
• Unexpected footer.
• Unknown double type.

AI-assisted analysis of icsharpcode/ILSpy@60c08fcb74 (2026-08-13). Data as JSON: /api/errors/fad3036ae570593d. Report an issue: GitHub.

Appendix: source

Thrown at ICSharpCode.BamlDecompiler/Baml/BamlReader.cs:273

					case BamlRecordType.EndAttributes:
					case BamlRecordType.DefTag:
					case BamlRecordType.ClrEvent:
					case BamlRecordType.Comment:
					default:
						throw new NotSupportedException();
				}
				rec.Position = pos;

				rec.Read(reader);
				ret.Add(rec);
				recs.Add(pos, rec);
			}
			for (int i = 0; i < ret.Count; i++)
			{
				if (ret[i] is IBamlDeferRecord defer)
					defer.ReadDefer(ret, i, offset => recs.TryGetValue(offset, out var rec)
						? rec
						: throw new InvalidDataException("BAML defer record points at an offset that is not a record boundary."));
			}

			return ret;
		}
	}
}

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