I can't get that constructor to work either. This however seems to work:

# $temp = Get-ResourceFiles
$resourceFiles = New-Object System.Collections.ArrayList($null)
$resourceFiles.AddRange($temp)

You can also pass an integer in the constructor to set an initial capacity.

What do you mean when you say you want to enumerate the files? Why can't you just filter the wanted values into a fresh array?

Edit:

It seems that you can use the array constructor like this:

$resourceFiles = New-Object System.Collections.ArrayList(,$someArray)

Note the comma. I believe what is happening is that when you call a .NET method, you always pass parameters as an array. PowerShell unpacks that array and passes it to the method as separate parameters. In this case, we don't want PowerShell to unpack the array; we want to pass the array as a single unit. Now, the comma operator creates arrays. So PowerShell unpacks the array, then we create the array again with the comma operator. I think that is what is going on.

You have several options:

$users | Where-Object {$Admin_User_Strings -contains $_.Description}

or: $users | Where-Object $_.Description -in $Admin_User_Strings

or: $users | Where-Object $_.Description -match "adm|admin|administrator"

try Something like this:

$array1=import-csv "C:\temp\log.csv"
$array2=import-csv "C:\temp\log2.csv"

#modify founded and output not founded
$toadd=$array2 | %{
$current=$_
$founded=$array1 | where pc -eq $current.pc | %{$_.date=$current.date;$_}

    if ($founded -eq $null)
    {
      $current.city='UNKNOW' 
      $current 
    }
}

#output of $array1 modified and elements to add
$array1, $toadd