Update Arrays In Powershell

<#-->The first 4 lines are the same for all attempts.  Between attempts I exited PowerShell.
I know I could use the Remove-Variable command too.<--#>
$Date = Get-Date -DisplayHint Date
Get-ADUser -Filter * -SearchBase "OU=Users,DC=Domain" -SearchScope OneLevel -Properties sAMAccountName |
Select-Object @{Name="User ID";Expression={$_."sAMAccountName"}}, @{Name="Date";Expression={$Date}} |
Export-Csv "C:\File.csv" -NoTypeInformation


#-->First Attempt<--#
$Import = Import-Csv C:\File.csv
$Sample = Get-Random -InputObject $Import -Count 20
$List = $Import -ne $Sample

#This shows 20.
$Sample.Count

#These both show the same number instead of $List being 20 less than $Import.
$Import.Count
$List.Count


#-->Second Attempt<--#
$Import = Get-Content C:\File.csv
$Sample = Get-Random -InputObject $Import -Count 20
$List = $Import -ne $Sample

#This shows 20.
$Sample.Count

#These both show the same number instead of $List being 20 less than $Import.
$Import.Count
$List.Count


#-->Third Attempt<--#
[System.Collections.ArrayList]$Import = Import-Csv C:\File.csv
[System.Collections.ArrayList]$Sample = Get-Random -InputObject $Import -Count 20
[System.Collections.ArrayList]$List = $Import -ne $Sample

#This shows 20.
$Sample.Count

#These both show the same number instead of $List being 20 less than $Import.
$Import.Count
$List.Count

#-->Fourth Attempt<--#
[System.Collections.ArrayList]$Import = Import-Csv C:\File.csv
[System.Collections.ArrayList]$Sample = Get-Random -InputObject $Import -Count 20
[System.Collections.ArrayList]$List = $Import.Remove($Sample)

#This shows 20.
$Sample.Count

#This shows 1000.
$Import.Count

#This shows 0.
$List.Count