@Tusharh
If you want the value of the registry entry "TaskCache" you should use QSettings::value(QString key) QObject::property(QString name) gives you the property of your QSettings object

@GoranShekerov
Tried the above code to stop and remove the windows service while uninstalling from QT installer. But did not work

function Controller()
{
installer.uninstallationStarted.connect(onUninstallationStarted);
}

onUninstallationStarted = function()
{
if (installer.isUninstaller()) {
installer.performOperation("Execute", "@TargetDir@/platform/tools/Server/testServer.exe", "stop");
console.log("Server stopped")
installer.performOperation("Execute", "@TargetDir@/platform/tools/Server/testServer.exe", "remove");
console.log("Server removed")
}
}