Powershell: Comparing Array (-notcontains) will not work

Question

I want to compare two Lists of Arrays and to display the Delta in a third array:

$ListOfVMs
$ListOfRunningVMs

$StoppedVMs = $ListOfVMs | { Where-Object $_.Name -notcontains $ListOfVMs.Name }

This Filter delivers still the complete Content of $ListOfVMs and not only the Delta. What I am doing wrong?

question from:https://stackoverflow.com/questions/66048635/powershell-comparing-array-notcontains-will-not-work

Answer 1

You may do the following:

$StoppedVMs = $ListOfVMs | Where-Object Name -notin $ListOfRunningVMs.Name

You need to pipe to Where-Object. Where-Object is what contains the script block (if you need to use it). You are also not comparing both lists here as you only reference $ListOfVMs.

Since you are comparing a single item against a collection, you will want to use -notin if the single item is on the left-hand side (LHS). -notcontains would be used if the collection is on the LHS.