bool XPackageUpdateInstallationMonitor(  
         XPackageInstallationMonitorHandle installationMonitor  
)  

bool CheckIfInstalled(XPackageInstallationMonitorHandle monitor)
{
    XPackageInstallationProgress progress;
    XPackageGetInstallationProgress(monitor, &progress);

    if (!progress.completed && XPackageUpdateInstallationMonitor(monitor))
    {
        XPackageGetInstallationProgress(monitor, &progress);
    }

    if (progress.completed)
    {
        XPackageCloseInstallationMonitorHandle(monitor);
    }

    return progress.completed;
}