How to create multiple arrays by a loop

I'm using a SQL module to pull data from a database inside Powershell.  The query returns object instances with two properties; PkgID and Content_ID.   There will be numerous Content_ID which each Content_ID being unique inside numerous PackageIDs.  For example, here's a typical output:

PkgID          Content_ID
UNH001          1234
UNH001          5935
UNH004          9532
UNH005          58390
UNH004          68402


What I'd like to do is get this output into a hash table with an array for each PkgID with output like this:


PkgID          Content_ID
UNH001          @(1234,5935)
UNH004          @(9532,68402)
UNH005          @(58390)


I'm thinking I can loop over the result set and do this dynamically but I can't figure out how.  Can anyone shed some light?

Yes, I know this is an old post, I’m trying to clean up older posts that are unanswered.
Did you ever figure this out?

 #### TESTDATA ####
 $results = @()
$pkgs = "" | Select PkgID, ContentID
$pkgs.PkgID = "UNH001"
$pkgs.ContentID = "1234"
$results += $pkgs
 $pkgs = "" | Select PkgID, ContentID
$pkgs.PkgID = "UNH001"
$pkgs.ContentID = "5935"
$results += $pkgs
 $pkgs = "" | Select PkgID, ContentID
$pkgs.PkgID = "UNH004"
$pkgs.ContentID = "9532"
$results += $pkgs
 $pkgs = "" | Select PkgID, ContentID
$pkgs.PkgID = "UNH004"
$pkgs.ContentID = "58390"
$results += $pkgs
 $pkgs = "" | Select PkgID, ContentID
$pkgs.PkgID = "UNH005"
$pkgs.ContentID = "68402"
$results += $pkgs
 #### END TESTDATA ####
 ########### You need the following bit #########
 $newresults = @{} # Create the hashtable
 $results | %{
  $arr = @()
  if ($newresults.containsKey($_.PkgID)) {  # If we have already added the pkgid to the table get it
    $arr = $newresults[$_.PkgID]                 # Retrieve the array
    $arr += $_.ContentID
    $newresults.Set_Item($_.PkgID,$arr)    # Overwrite the item with the new data
  } else {                                                     # else create it
    $arr += $_.ContentID
    $newresults.Add($_.PkgID, $arr)
  }
}
 ######################
 $newresults
  
 

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