private List <string> GetUserPhotos(User userPhoto) { List <Photo> fileList = new List <Photo>(); lock (Users) { foreach (User user in Users) { if (userPhoto.Equals(user)) { fileList = user.Photos; } } } List <string> result = new List <string>(); if (fileList.Count == 0) { return(null); } foreach (Photo photo in fileList) { result.Add(photo.ToString()); } return(result); }