public void saveBinaryFile(ObservableCollection <User> Users) { SaveFileDialog saveFileDialog = new SaveFileDialog(); saveFileDialog.FileName = "users.bin"; saveFileDialog.DefaultExt = ".bin"; saveFileDialog.Filter = "Binary documents (.bin)|*.bin"; var result = saveFileDialog.ShowDialog(); if (result == true) { writer.Create(saveFileDialog.FileName); foreach (var u in Users) { PublicUsers.Add(new UserAbstraction { ID = u.ID, LastName = u.LastName, Name = u.Name, SecondName = u.SecondName, Email = u.Email }); } writer.Write(PublicUsers); } }