public IEnumerable <List <Reference> > FindAllReferences(string refString) { var refsList = new ConcurrentBag <List <Reference> >(); var files = Project.GetProjectFiles(); Task.WaitAll(files.Select(file => Project.ProjectDirectory.Combine(file.FileFullPath)) .Select(filePath => Task.Factory.StartNew(() => { var refs = _parserService.FindAllReferencesInFile(filePath, refString); if (refs.Any()) { refsList.Add(refs); } })).ToArray()); return(refsList); }