icsharpcode/ILSpy · error · BadImageFormatException

Expected a TypeDef, TypeRef or TypeSpec handle!

Error message

Expected a TypeDef, TypeRef or TypeSpec handle!

What it means

BadImageFormatException while disassembling an event: the event's .type handle must be a TypeDefinition, TypeReference, or TypeSpecification. Any other HandleKind means corrupt EventMap/Event table metadata, so the signature cannot be decoded.

Source

Thrown at ICSharpCode.Decompiler/Disassembler/ReflectionDisassembler.cs:1555

			WriteMetadataToken(output, module, handle, MetadataTokens.GetToken(handle),
				spaceAfter: true, spaceBefore: true, ShowMetadataTokens, ShowMetadataTokensInBase10);
			WriteFlags(eventDefinition.Attributes, eventAttributes, output);
			var provider = new DisassemblerSignatureTypeProvider(module, output);
			Action<ILNameSyntax> signature;
			switch (eventDefinition.Type.Kind)
			{
				case HandleKind.TypeDefinition:
					signature = provider.GetTypeFromDefinition(module.Metadata, (TypeDefinitionHandle)eventDefinition.Type, 0);
					break;
				case HandleKind.TypeReference:
					signature = provider.GetTypeFromReference(module.Metadata, (TypeReferenceHandle)eventDefinition.Type, 0);
					break;
				case HandleKind.TypeSpecification:
					signature = provider.GetTypeFromSpecification(module.Metadata, new MetadataGenericContext(declaringType, module),
						(TypeSpecificationHandle)eventDefinition.Type, 0);
					break;
				default:
					throw new BadImageFormatException("Expected a TypeDef, TypeRef or TypeSpec handle!");
			}
			signature(ILNameSyntax.TypeName);
			output.Write(' ');
			output.Write(DisassemblerHelpers.Escape(module.Metadata.GetString(eventDefinition.Name)));
		}
		#endregion

		#region Disassemble Type
		internal static readonly EnumNameCollection<TypeAttributes> typeVisibility = new EnumNameCollection<TypeAttributes>() {
			{ TypeAttributes.Public, "public" },
			{ TypeAttributes.NotPublic, "private" },
			{ TypeAttributes.NestedPublic, "nested public" },
			{ TypeAttributes.NestedPrivate, "nested private" },
			{ TypeAttributes.NestedAssembly, "nested assembly" },
			{ TypeAttributes.NestedFamily, "nested family" },
			{ TypeAttributes.NestedFamANDAssem, "nested famandassem" },
			{ TypeAttributes.NestedFamORAssem, "nested famorassem" },
		};

View on GitHub (pinned to 60c08fcb74)

Solutions

1. Catch BadImageFormatException around DisassembleEvent and skip the offending event.
2. Validate the assembly with peverify and obtain a clean copy.

try {
    disassembler.DisassembleEvent(module, eventHandle);
} catch (BadImageFormatException ex) {
    logger.Warning("Corrupt event metadata in {Module}: {Message}", module.FileName, ex.Message);
}

When it happens

Trigger: Disassembling an event whose EventType column points at a handle that is not a TypeDef/Ref/Spec: truncated or malformed metadata.

Common situations: Corrupt or obfuscated assemblies; PE files produced by broken tooling.

Related errors

• Unexpected rawTypeKind: {rawTypeKind} (0x{rawTypeKind:x})
• Implementation must either be an index into the File, Export
• Cannot get RVA section prefix from module
• types contains null element
• Could not find type definition {fullTypeName} in type system

AI-assisted analysis of icsharpcode/ILSpy@60c08fcb74 (2026-08-13). Data as JSON: /api/errors/17425fa85204820b. Report an issue: GitHub.