Passing arguments as a variable when installing an MSI using Start-Process - powershell

Question

I am new to Powershell and, of course, trying to learn on the fly for a project- No pressure, right! :-)
I am working on a script to run an MSI package in quiet mode, passing it an activation code as an argument, that I have to extract from an XML file.
So far, I have everything working except for getting Start-Process to run the MSI with the arguments being passed in a Variable.
Set-ExecutionPolicy Bypass -Force
[System.Xml.XmlDocument]$XML_Doc = new-object System.Xml.XmlDocument
$XML_Doc.load('c:\myfolder\Configinfo.XML')
$ActivationID = $XML_Doc.CONFIGINFO.SITEINFO.ACTIVATEID
write-host "Activation Id is: $ActivationID"
$InstallString = "`'/I C:\myfolder\myinstaller.msi akey="+'"'+$ActivationID+'"'''
#$InstallString = "`'/I C:\myfolder\myinstaller.msi akey=`"$($ActivationID)`"'"
write-host "$InstallString"'''
Start-Process msiexec.exe -ArgumentList $InstallString -Wait -NoNewWindow
#Start-Process msiexec.exe -ArgumentList '/I C:\myfolder\myinstaller.msi akey="12345678-abcd-1a1b-x9x1-a1b2c3d4e5f6"' -Wait -NoNewWindow
Above is the code I am working with now. The last line that is commented out is an activation string that works.
I have verified that $ActivationID is pulling back the correct value, and that $InstallString mirrors the argument list in the commented version of the Start-Process string.
Any help would be appreciated!

Answer 1

The Start-Process commands aren't necessary. PowerShell is a shell. It can run commands. Just put the commands you want to run directly in the script.
msiexec /i "C:\myfolder\myinstaller.msi" "AKEY=$ActivationID"
I quoted the parameters to msiexec.exe in case any of them contain spaces. PowerShell will automatically expand the $ActivationID variable into the string inside the double quotes.

Answer 2

Your ArgumentList is being passed incorrectly.
[Xml]$XML_Doc = Get-Content -Path 'C:\myfolder\Configinfo.xml'
$ActivationID = $XML_Doc.CONFIGINFO.SITEINFO.ACTIVATEID
Write-Host "Activation Id is: $ActivationID"
$Path = 'msiexec'
$ArgList = #('/i','"C:\path\file.msi"',"akey=`"$ActivationID`"")
Write-Host "$Path $ArgList"
Start-Process -FilePath $Path -ArgumentList $ArgList -Wait -NoNewWindow

Answer 3

First off, let me welcome you to Powershell! It's a great language and a great community gathered around a common cause.
Since you're new to the language, you can still learn new tricks and that's a good thing, because it's generally accepted that the Write-Host cmdlet is nearly always a poor choice. If you don't trust me, you should trust the inventor of Powershell.
Now that that's out of the way, we should look at your MSI command. With Powershell, we don't have to directly open msiexec, and we can call the MSI directly. I would break the path to the installer into its own variable, and then we can add all of our arguments on top of it. Also, don't forget the "/qn" switch which will actually make all of this silent. All in all, your new script will look something like this:
[System.Xml.XmlDocument]$XML_Doc = new-object System.Xml.XmlDocument
$XML_Doc.load('c:\myfolder\Configinfo.XML')
$ActivationID = $XML_Doc.CONFIGINFO.SITEINFO.ACTIVATEID
Write-Verbose "Activation Id is: $ActivationID"
$msipath = "C:\myfolder\myinstaller.msi"
$args = #("akey=$ActivationID", "/qn")
Write-Verbose "Install path is $msipath"
Write-Verbose "Activation key is $akey"
Start-Process $msipath -ArgumentList $args -Wait -NoNewWindow