icsharpcode/ILSpy · error · ReflectionNameParseException

Could not find '.' separating type name from member name

Error message

Could not find '.' separating type name from member name

What it means

ReflectionNameParseException at position 0 thrown by FindEntity(string, ITypeResolveContext) on the member path when FindMemberNameDot returns a value <= 2. A member ID string must contain a '.' that separates the declaring type name from the member name (e.g. 'M:System.Console.WriteLine'); with no dot after the 'X:' prefix there is no member name to resolve.

Source

Thrown at ICSharpCode.Decompiler/Documentation/IdStringProvider.cs:744

		/// <param name="idString">ID string of the entity.</param>
		/// <param name="context">Type resolve context</param>
		/// <returns>Returns the entity, or null if it is not found.</returns>
		/// <exception cref="ReflectionNameParseException">The syntax of the ID string is invalid</exception>
		public static IEntity FindEntity(string idString, ITypeResolveContext context)
		{
			if (idString == null)
				throw new ArgumentNullException(nameof(idString));
			if (context == null)
				throw new ArgumentNullException(nameof(context));
			if (idString.Length < 2 || idString[1] != ':')
				throw new ReflectionNameParseException(0, "Missing type tag");

			if (idString[0] == 'T')
				return FindTypeDefinition(idString.Substring(2), context);

			int dotPos = FindMemberNameDot(idString);
			if (dotPos <= 2)
				throw new ReflectionNameParseException(0, "Could not find '.' separating type name from member name");
			var declaringType = FindTypeDefinition(idString.Substring(2, dotPos - 2), context);
			if (declaringType?.ParentModule is not MetadataModule metadataModule)
				return null;
			var typeDef = metadataModule.MetadataFile.Metadata.GetTypeDefinition(
				(TypeDefinitionHandle)declaringType.MetadataToken);
			var handle = FindMemberInType(metadataModule.MetadataFile, typeDef, idString[0], idString);
			return handle.IsNil ? null : metadataModule.ResolveEntity(handle);
		}

		/// <summary>
		/// Resolves a type name from an ID string (without the "T:" prefix) in the given
		/// type resolve context, trying all namespace/type-name boundary splits.
		/// </summary>
		static ITypeDefinition FindTypeDefinition(string typeName, ITypeResolveContext context)
		{
			var parts = ParseTypeNameParts(typeName);
			string[] dotParts = parts[0].Name.Split('.');

View on GitHub (pinned to 60c08fcb74)

Solutions

1. Provide the full member ID including the declaring type and member name separated by '.', e.g. "M:System.Console.WriteLine".
2. For type lookups use the 'T:' tag so the member path is not taken.
3. Validate that the substring after 'X:' contains a '.' before calling.

Example fix

// before
var e = IdStringProvider.FindEntity("M:System.Console", context);

// after
var e = IdStringProvider.FindEntity("M:System.Console.WriteLine", context);

if (idString[0] == 'T') return IdStringProvider.FindEntity(idString, context);
int dot = idString.LastIndexOf('.', Math.Max(0, (idString.IndexOf('(') is int p && p >= 0 ? p : idString.Length) - 1));
if (dot <= 2) return null; // no member name
return IdStringProvider.FindEntity(idString, context);

static bool IsMemberIdString(string s) => s != null && s.Length >= 2 && s[1] == ':' && "MFPE".IndexOf(s[0]) >= 0 && s.LastIndexOf('.') > 2;

try { return IdStringProvider.FindEntity(idString, context); }
catch (ReflectionNameParseException ex) { logger.Warn($"Bad member ID string at {ex.Position}: {ex.Message}"); return null; }

When it happens

Trigger: Calling FindEntity with a member-tagged string that has no member name, e.g. "M:Console", "F:System.Console", or any 'M:'/'F:'/'P:'/'E:' string whose only dot (if any) sits at index <= 2.

Common situations: Truncating an ID string after the type name; passing a type ID into a member lookup; hand-built crefs that omit the member.

Related errors

• Missing type tag
• Expected type name
• Expected '}'
• The handle must not be nil.
• Unsupported handle kind: {handle.Kind}

AI-assisted analysis of icsharpcode/ILSpy@60c08fcb74 (2026-08-13). Data as JSON: /api/errors/7c8cc17a4901d0d6. Report an issue: GitHub.