string connstr = "server=localhost; user=root; database=users_db; password=0000";
MySqlConnection conn = new MySqlConnection(connstr);
string sql_registrUser = "INSERT INTO `users_db`.`users` (`user_login`, `user_password`) VALUES ('" + login + "', '" + password + "');";
MySqlCommand comm_registr = new MySqlCommand(sql_registrUser, conn);