Powershell: Filter Hashtable - and get back a Hastable

Question

Filtering a Hashtable using GetEnumerator always returns a object[] instead of a Hashtable:

# Init Hashtable
$items = @{ a1 = 1; a2 = 2; b1 = 3; b2 = 4}
# apply a filter
$filtered = $items.GetEnumerator() | ?{ $_.Key -match "a.*" }
# The result looks great
$filtered
  Name                           Value
  ----                           -----
  a2                             2
  a1                             1
# … but it is not a Hashtable :-(
$filtered.GetType()
  IsPublic IsSerial Name                                     BaseType
  -------- -------- ----                                     --------
  True     True     Object[]                                 System.Array

Is there a nice solution to this problem?

Thanks a lot for any Help!, kind regards, Tom

Answer 1

$filtered is an array of dictionary entries. There's no single cast or ctor for this as far as I know.

You can construct a hash though:

$hash = @{}
$filtered | ForEach-Object { $hash.Add($_.Key, $_.Value) }

Another workflow:

# Init Hashtable
$items = @{ a1 = 1; a2 = 2; b1 = 3; b2 = 4}

# Copy keys to an array to avoid enumerating them directly on the hashtable
$keys = @($items.Keys)
# Remove elements not matching the expected pattern
$keys | ForEach-Object {
    if ($_ -notmatch "a.*") {
        $items.Remove($_)
    }
}

# $items is filtered