How to get the "difference" between two objects in another object with the same structure using powershell?

TL;DR: This but in powershell
I’m trying to get the "difference" between a list1 and a list2 where list2 is just a sub-set of list1. (or list1 is a super-set of list2).

Keep in mind that this is not the ‘real scenario’ but the structures of both objects are the same as this:

#List of all the IDs
$list1='2','5','6','11'
$CustObject1=foreach($i in $list1){
    [pscustomobject]@{
        id=$i
    }
}
#Another list, where invalid IDs are not listed
$list2='2','5'
$CustObject2=foreach($i in $list2){
    [pscustomobject]@{
        id=$i
    }
}
#I am looking for $CustObject3 = {id = '6',id = '11'}

Now, I want to create a new "object" that contains a list of all the ‘invalid’ IDs, in our example the $CustObject3 would contain just id’s '6','11'.
The reason behind this is because I have a list of 3000 ids that are "valid" and just a couple that are "invalid" (at most 10).
I’ve tried a lot of options but I can’t get it to work, used "where", used double foreach loops, honestly I’m just frustrated at this point but I did try to make it work.

Is this feasible?

Thanks.

>Solution :

You can use the -notin or -notcontains operators to perform the check.

#List of all the IDs
$list1='2','5','6','11'
$CustObject1=foreach($i in $list){
    [pscustomobject]@{
        id=$i
    }
}
#Another list, where invalid IDs are not listed
$list2='2','5'
$CustObject2=foreach($i in $list){
    [pscustomobject]@{
        id=$i
    }
}

$CustomObject1 | Where-Object {$_.id -notin $CustomObject2.id}