icsharpcode/ILSpy · error · ArgumentNullException

definitions

Error message

definitions

What it means

ArgumentNullException(nameof(definitions)) from Decompile(IEnumerable<EntityHandle>) when the definitions sequence is null. The public Decompile(params EntityHandle[]) overload forwards to this one, so passing null there lands here too.

Source

Thrown at ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs:1369

		{
			return SyntaxTreeToString(DecompileType(fullTypeName));
		}

		/// <summary>
		/// Decompile the specified types and/or members.
		/// </summary>
		public SyntaxTree Decompile(params EntityHandle[] definitions)
		{
			return Decompile((IEnumerable<EntityHandle>)definitions);
		}

		/// <summary>
		/// Decompile the specified types and/or members.
		/// </summary>
		public SyntaxTree Decompile(IEnumerable<EntityHandle> definitions)
		{
			if (definitions == null)
				throw new ArgumentNullException(nameof(definitions));
			syntaxTree = new SyntaxTree();
			var namespaces = new HashSet<string>();
			foreach (var entity in definitions)
			{
				if (entity.IsNil)
					throw new ArgumentException("definitions contains null element");
				RequiredNamespaceCollector.CollectNamespaces(entity, module, namespaces);
			}
			var decompileRun = CreateDecompileRun(namespaces);

			bool first = true;
			ITypeDefinition? parentTypeDef = null;
			foreach (var entity in definitions)
			{
				switch (entity.Kind)
				{
					case HandleKind.TypeDefinition:
						ITypeDefinition typeDef = module.GetDefinition((TypeDefinitionHandle)entity);

View on GitHub (pinned to 60c08fcb74)

Solutions

1. Pass a non-null collection; use Array.Empty<EntityHandle>() instead of null for the empty case.
2. Null-coalesce at the call site: decompiler.Decompile(handles ?? Array.Empty<EntityHandle>()).

Example fix

// before
SyntaxTree tree = decompiler.Decompile(handles); // handles may be null

// after
SyntaxTree tree = decompiler.Decompile(handles ?? Array.Empty<EntityHandle>());

var tree = decompiler.Decompile(handles ?? Array.Empty<EntityHandle>());

When it happens

Trigger: Calling Decompile((IEnumerable<EntityHandle>)null), Decompile((EntityHandle[])null), or passing a variable that is null because a preceding lookup returned no array.

Common situations: A LINQ/mapping step returns null on the empty case instead of an empty collection; an uninitialized EntityHandle[] field passed straight through.

Related errors

• types contains null element
• definitions contains null element
• handle
• HandleKind {handle.Kind} is not supported!
• Invalid BAML signature length.

AI-assisted analysis of icsharpcode/ILSpy@60c08fcb74 (2026-08-13). Data as JSON: /api/errors/cfe4ab3087faf980. Report an issue: GitHub.