Работа с текстовым файлом C#

 StreamWriter usersFile = new StreamWriter("users.txt", true); 
 ...
 foreach (string currUch in uchItems)
                {
                    pwd = pwdUch.GetPassword().ToString();
                    MySqlCommand addUch = new MySqlCommand(AddSchoolQuery(currUch, pwd, "%"), armSchoolCon);
                    addUch.ExecuteNonQuery();
                    usersFile.WriteLine(currUch + '\t' + pwd + '\n');
                    MySqlCommand delUch = new MySqlCommand("DELETE FROM uch_turn WHERE kod_uch='" + currUch + "';", armSchoolCon);
                    delUch.ExecuteNonQuery();
                }