private void AddExterns( ref CompilationUnitSyntax root, ref NamespaceDeclarationSyntax namespaceToUpdate, ExternAliasDirectiveSyntax externAliasDirective) { if (namespaceToUpdate != null) { namespaceToUpdate = namespaceToUpdate.AddExterns(externAliasDirective); } else { root = root.AddExterns(externAliasDirective); } }