public List <string> OutputAsStringList() { List <string> output = new List <string>(); output.Add("___________________________________________________________"); int lineNumber = 1; foreach (string line in Listing) { output.Add(lineNumber++.ToString("d5") + " " + line); } output.Add("___________________________________________________________"); output.Add(" "); return(output.Concat(programData.OutputAsStringList()).ToList()); }