Powershell script with Contains operator not working - powershell

Question

I am completely stuck! Hoping someone can help point out what I'm doing wrong. PS script below.
For testing I have 2 users in "newusers.csv" and the same 2 users in "currentmembers.csv". These are teh same file just renamed. Results of script are that the 2 users in "newusers.csv" are NOT members of "currentmembers.csv". This is obviously wrong but I can't figure out what is wrong with the script.
$list = Import-Csv newusers.csv
$members = Import-Csv currentmembers.csv
foreach ($UPN in $list) {
If ($members-Contains $UPN.upn) {
Write-Host $UPN.upn "is member"
} Else {
Write-Host $UPN.upn "is not a member"
}}
Results
user 1 is not a member
user 2 is not a member

Answer 1

Your two Import-CSV calls are creating an array of objects, each containing two objects with 1 value (UPN). Your use of -contains will not work here as, you are not comparing directly to a string, more info here.
You have two options.
#1 you can use -in
foreach ($UPN in $list) {
If ($UPN.upn -in $members.upn) {
Write-Host $UPN "is member"
}
Else {
Write-Host $UPN "is not a member"
}
}
#2 You can use -match
foreach ($UPN in $list) {
If ($members -match $UPN.upn) {
Write-Host $UPN.upn "is member"
}
Else {
Write-Host $UPN.upn "is not a member"
}
}

Answer 2

Completely agree with Owain's answer, but I got halfway through mine so I thought I'd finish it. You can try playing with sample data directly in PowerShell as follows, using ConvertFrom-Csv, which saves you editing files and then hopping back into PowerShell:
$list = #'
upn
user 1
user 2
user 7
user 99
'# | ConvertFrom-Csv
$members = #'
upn
user 2
user 1
user 4
'# | ConvertFrom-Csv
foreach ($UPN in $list) {
If ($UPN.upn -in $members.upn) {
Write-Host $UPN.upn "is member"
} Else {
Write-Host $UPN.upn "is not a member"
}}
As Owain said, you need to alter the comparison part to compare a string to an array.

Answer 3

Your $member should be an array of strings, not array of objects. Same thing as you are comparing $upn.UPN - the $upn is a object and you're accessing UPN member of it.
Hope that I explained this clearly
$members = Import-Csv currentmembers.csv | select -expandproperty ColumnName