gugoeb,
Welcome to the forum. 
In PowerShell we work with objects and properties. To compare objects we use
For your requirement it would be something like this:
$Array1 = @'
ObjectID
1
2
3
4
5
'@ |
ConvertFrom-Csv
$Array2 = @'
ObjectID
1
3
5
6
7
'@ |
ConvertFrom-Csv
Compare-Object -ReferenceObject $Array1 -DifferenceObject $Array2 -Property ObjectID -PassThru |
Where-Object -Property SideIndicator -EQ -Value '<='
And BTW: When you post code please format it as code using the preformatted text button ( </> ). Simply place your curseor on an empty line, click the button and paste your code.
Thanks in advance