How to check for a pending restart

[extony]

I have a Custom BA that creates my software's MSI, a custom Burn UI, and a bootstrapper that bundles a few prerequisites for my software. I have some users having issues when installing with my installer. Their issue seems to be that their machine needs to be restarted before running the installer. After they restart their machine, that seems to resolve their issues. Not a common issue, but I would still like to resolve this. I have not found much straightforward information online about how to resolve this. I have this following code in my Custom BA:

private bool IsRebootRequired()
{
// Check Pending File Rename Operations
using (var sessionManager = Registry.LocalMachine.OpenSubKey(@"SYSTEM\CurrentControlSet\Control\Session Manager"))
{
if (sessionManager != null && sessionManager.GetValue("PendingFileRenameOperations") != null)
{
return true;
}
}

// Check Windows Update RebootRequired key
using (var windowsUpdate = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update"))
{
    if (windowsUpdate != null && windowsUpdate.GetValue("RebootRequired") != null)
    {
        return true;
    }
}

return false;

}

I then use this method first thing in the "Run" method:
// Check for pending reboot
if (IsRebootRequired())
{
this.Engine.Log(LogLevel.Error, "A pending reboot has been detected. Installation cannot proceed.");
System.Windows.MessageBox.Show(
"A system reboot is required before running this installation. Please restart your computer and try again.",
"Restart Required",
System.Windows.MessageBoxButton.OK,
System.Windows.MessageBoxImage.Warning);

            this.Engine.Quit(-1); // Exit with an error code
            return;
        }

There seems to always be some internet files or other values in the PendingFileRenameOperations that do not matter. Does anyone have a solution for this? Not sure how other installers check if the machine needs a restart before installing. I am somewhat new to the WiX community so any resources or direction would be greatly appreciated

[wldevries]

You can use the RebootPending variable to check this.
https://wixtoolset.org/docs/tools/burn/builtin-variables/

IEngine.GetVariableString("RebootPending") != "0"

We've had bad experiences with this approach though, where a reboot is almost always pending. Most probably false positives. This might be related to a change in functionality in Wix 4. I don't understand what they mean here:

The built-in variable RebootPending is also reset everytime during Detect.

https://wixtoolset.org/docs/fourthree/faqs/#timing-changes-for-detection