icsharpcode/ILSpy · error · InvalidDataException

Unknown double type.

Error message

Unknown double type.

What it means

Thrown by XamlUtils.ReadXamlDouble (in non-scaledInt mode). The first byte is a discriminator: 1->0, 2->1, 3->-1, 4->int-scaled, 5->raw double; any other value raises InvalidDataException('Unknown double type.'). It is hit while reading geometry/point/vector data for the path and collection serializers.

Source

Thrown at ICSharpCode.BamlDecompiler/Xaml/XamlUtils.cs:79

		public static double ReadXamlDouble(this BinaryReader reader, bool scaledInt = false)
		{
			if (!scaledInt)
			{
				switch (reader.ReadByte())
				{
					case 1:
						return 0;
					case 2:
						return 1;
					case 3:
						return -1;
					case 4:
						break;
					case 5:
						return reader.ReadDouble();
					default:
						throw new InvalidDataException("Unknown double type.");
				}
			}
			// Dividing by 1000000.0 is important to get back the original numbers, we can't
			// multiply by the inverse of it (0.000001).
			// (11700684 * 0.000001) != (11700684 / 1000000.0) => 11.700683999999999 != 11.700684
			return reader.ReadInt32() / 1000000.0;
		}

		/// <summary>
		/// Escape characters that cannot be used in XML.
		/// </summary>
		public static StringBuilder EscapeName(StringBuilder sb, string name)
		{
			foreach (char ch in name)
			{
				if (char.IsWhiteSpace(ch) || char.IsControl(ch) || char.IsSurrogate(ch))
					sb.AppendFormat("\\u{0:x4}", (int)ch);
				else

View on GitHub (pinned to 60c08fcb74)

Solutions

1. Inspect the bytes at the failure point to see the invalid discriminator.
2. Re-extract the resource from a clean assembly.
3. Treat the resource as malformed.

try {
    SafeDecompile(bamlResource);
} catch (InvalidDataException ex) when (ex.Message == "Unknown double type.") {
    // malformed geometry/point data; skip the resource
}

When it happens

Trigger: BAML path/point/vector/3D collection data where the per-double discriminator byte is not in {1,2,3,4,5}.

Common situations: Corrupted geometry or point-collection data; a new double-encoding variant; truncated serializer payload.

Related errors

• Unexpected footer.
• {type}
• {ser}
• Invalid BAML signature length.
• BAML defer record points at an offset that is not a record b

AI-assisted analysis of icsharpcode/ILSpy@60c08fcb74 (2026-08-13). Data as JSON: /api/errors/455c473b3c5f9239. Report an issue: GitHub.