public static IWorkWithFiles findExtention(string path) { IWorkWithFiles fileOperation; string extention = (path.Substring(path.LastIndexOf('.') + 1)).ToString(); switch (extention) { case "csv": fileOperation = new CSVFiles(); break; case "yaml": fileOperation = new YAMLFiles(); break; case "json": fileOperation = new JSONFiles(); break; default: fileOperation = new XMLFiles(); break; } return fileOperation; }