private void AddUsingDirective( ref CompilationUnitSyntax root, ref NamespaceDeclarationSyntax namespaceToUpdate, bool placeSystemNamespaceFirst, UsingDirectiveSyntax usingDirective) { IList <UsingDirectiveSyntax> directives = new[] { usingDirective }; if (namespaceToUpdate != null) { namespaceToUpdate = namespaceToUpdate.AddUsingDirectives( directives, placeSystemNamespaceFirst); } else { root = root.AddUsingDirectives( directives, placeSystemNamespaceFirst); } }