PSCustomObject to Hashtable

Shouldn't be too hard. Something like this should do the trick:

# Create a PSCustomObject (ironically using a hashtable)
$ht1 = @{ A = 'a'; B = 'b'; DateTime = Get-Date }
$theObject = new-object psobject -Property $ht1

# Convert the PSCustomObject back to a hashtable
$ht2 = @{}
$theObject.psobject.properties | Foreach { $ht2[$_.Name] = $_.Value }

Keith already gave you the answer, this is just another way of doing the same with a one-liner:

$psobject.psobject.properties | foreach -begin {$h=@{}} -process {$h."$($_.Name)" = $_.Value} -end {$h}

Here's a version that works with nested hashtables / arrays as well (which is useful if you're trying to do this with DSC ConfigurationData):

function ConvertPSObjectToHashtable
{
    param (
        [Parameter(ValueFromPipeline)]
        $InputObject
    )

    process
    {
        if ($null -eq $InputObject) { return $null }

        if ($InputObject -is [System.Collections.IEnumerable] -and $InputObject -isnot [string])
        {
            $collection = @(
                foreach ($object in $InputObject) { ConvertPSObjectToHashtable $object }
            )

            Write-Output -NoEnumerate $collection
        }
        elseif ($InputObject -is [psobject])
        {
            $hash = @{}

            foreach ($property in $InputObject.PSObject.Properties)
            {
                $hash[$property.Name] = ConvertPSObjectToHashtable $property.Value
            }

            $hash
        }
        else
        {
            $InputObject
        }
    }
}

My extremely lazy approach, enabled by a new feature in PowerShell 6:

$myhashtable = $mypscustomobject | ConvertTo-Json | ConvertFrom-Json -AsHashTable

This works for PSCustomObjects created by ConvertFrom_Json.

Function ConvertConvertFrom-JsonPSCustomObjectToHash($obj)
{
    $hash = @{}
     $obj | Get-Member -MemberType Properties | SELECT -exp "Name" | % {
                $hash[$_] = ($obj | SELECT -exp $_)
      }
      $hash
}

Disclaimer: I barely understand PowerShell so this is probably not as clean as it could be. But it works (for one level only).