Hashtables from ConvertFrom-json have different type from powershells built-in hashtables, how do I make them the same?

Here's a quick function to convert a PSObject back into a hashtable (with support for nested objects; intended for use with DSC ConfigurationData, but can be used wherever you need it).

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        }    }}

The ConvertFrom-Json cmdlet gives you a custom object so you have to access them using dot notation rather than as a subscript. Usually you would know what fields you expect in the JSON so this is actually more useful in general than getting a hash table. Rather than fighting the system by converting back to a hash table, I suggest you work with it.

You can use select with wildcard property names to get at the properties:

PS D:\> $data = @"{    "root":    {        "key":"value", "key2":"value2", "another":42    }}"@ | ConvertFrom-JsonPS D:\> $data.root | select * | ft -AutoSizekey   key2   another---   ----   -------value value2      42PS D:\> $data.root | select k* | ft -AutoSizekey   key2  ---   ----  value value2

and Get-Member if you want to extract a list of property names that you can iterate over:

PS D:\> ($data.root | Get-Member -MemberType NoteProperty).Nameanotherkeykey2

Putting that into a loop gives code like this:

PS D:\> foreach ($k in ($data.root | Get-Member k* -MemberType NoteProperty).Name) {    Write-Output "$k = $($data.root.$k)"    }key = valuekey2 = value2

The example was for a relatively shallow source object (not nested objects in the properties).

Here's a version that will go 2 levels deep into the source object, and should work with your data:

$data = @{}foreach ($propL1 in $x.psobject.properties.name)   {     $data[$propL1] = @{}     foreach ($propL2 in $x.$propL1.psobject.properties.name)        {          $data[$PropL1][$PropL2] = $x.$propL1.$propL2        }    }$data.root.keyskey