备份数据库时连接数据库出错,该如何解决

SQLDMO.Backup oBackup = new SQLDMO.BackupClass();
            SQLDMO.SQLServer oSQLServer = new SQLDMO.SQLServerClass();
            try
            {
                oSQLServer.LoginSecure = false;
                oSQLServer.Connect("127.0.0.1", "sa", "123");
                oBackup.Action = SQLDMO.SQLDMO_BACKUP_TYPE.SQLDMOBackup_Database;
                oBackup.Database = dbName;
                oBackup.Files = @"backup\" + backupDBName + ".bak";
                oBackup.BackupSetName = backupDBName;               
                oBackup.BackupSetDescription = "数据库备份";
                oBackup.Initialize = true;            
                oBackup.SQLBackup(oSQLServer);               
            }