Error on QODBC

[METEOR7]

Hi Everyone

I Get Error in ODBC when i open connect To DataBase
Error:

[Microsoft][ODBC Driver Manager] Data Source Name Not Found and No Default Driver
specified QODBC3: Unable To Connect

[Microsoft][ODBC Driver Manager] Data Source Name Not Found and No Default Driver
specified QODBC3: Unable To Connect

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and I Used This Code:

QString servername="LOCALHOST\\SQLEXPRESS";
    QString dbname="Test";
    QSqlDatabase db = QSqlDatabase::addDatabase("QODBC");
   db.setConnectOptions();
   QString dsn=QString("Driver=(SQL Native Client);SERVER=%1;DATABASE=%2;Trusted_Connection=Yes;").arg(servername).arg(dbname);
   db.setDatabaseName(dsn);
   if(db.open())
    {
        QMessageBox::about(this,"","OK");
    }
    QMessageBox::about(this,"",db.lastError().text());

QString servername="LOCALHOST\\SQLEXPRESS";
    QString dbname="Test";
    QSqlDatabase db = QSqlDatabase::addDatabase("QODBC");
   db.setConnectOptions();
   QString dsn=QString("Driver=(SQL Native Client);SERVER=%1;DATABASE=%2;Trusted_Connection=Yes;").arg(servername).arg(dbname);
   db.setDatabaseName(dsn);
   if(db.open())
    {
        QMessageBox::about(this,"","OK");
    }
    QMessageBox::about(this,"",db.lastError().text());

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Thanks