private static List <ProjectFile> ExtractSourceFiles(IEnumerable <ProjectItemGroup> items, ResourceType resourceType, ProjectFileBase project) { var files = new List <ProjectFile>(); if (items == null) { return(files); } foreach (var item in items) { var resource = ProjectFile.CreateIfValid(item, resourceType, project); if (resource != null) { files.Add(resource); } else { } } return(files); }