ex/importing multivalue registry keys in PowerShell via XML

Question

I'm having some trouble ex/importing registry values with PowerShell, specifically with multivalue (REG_MULTI_SZ) keys. I have a test registry entry:

[HKEY_CURRENT_USER\SOFTWARE\my\Testkey]
"string"="blub"
"multi"=hex(7):6f,00,6e,00,65,00,00,00,74,00,77,00,6f,00,00,00,74,00,68,00,72,\
  00,65,00,65,00,00,00,00,00
"bin"=hex:11,11,11,11,10

Now if I do the following

$Hive = "HKCU:\SOFTWARE\my\Testkey"
$Property = (Get-ItemProperty -path $Hive)
$Property.PSObject.Properties |
    select name, value, TypeNameOfValue |
    Where-Object name -NotLike "PS*" |
    Export-Clixml test.xml
$Prop = Import-Clixml .\test.xml 

foreach ($i in $Prop) {
    New-ItemProperty -Path $Hive -Name $i.Name -Value $i.Value 
}

The value of the key in the registry is set to "System.Collections.ArrayList" instead of its real value. It only seems to happen to multivalue keys.

I tried

New-ItemProperty -Path $Hive -Name $i.Name -Value ($i.Value | Out-String)

but that didn't work either. It seems like New-ItemProperty doesn't convert the string arrays into the proper type. Anyone any idea what datatype to use/how to fix this?

Obviously I can use

foreach($i in $Prop){
    if ($i.TypeNameOfValue -eq 'System.String[]') {
        New-ItemProperty -Path $Hive -Name $i.Name -Value $i.Value -PropertyType "MultiString"
    } else {
        New-ItemProperty -Path $Hive -Name $i.Name -Value $i.Value 
    }
}

but I'd prefer to just convert $i.Value to the proper datatype during ex- or import.

Or is there any other clever solution I overlooked?

Answer 1

You need to import the values with the correct type. Create a hashtable mapping the type of the imported data to the corresponding registry data type and look up the type name on import:

$regtypes = @{
    'System.String'   = 'String'
    'System.String[]' = 'MultiString'
    'System.Byte[]'   = 'Binary'
}

foreach ($i in $Prop) {
    New-ItemProperty -Path $Hive -Name $i.Name -Value $i.Value -Type $regtypes[$i.TypeNameOfValue]
}

An alternative would be casting the value to the imported type name:

foreach ($i in $Prop) {
    New-ItemProperty -Path $Hive -Name $i.Name -Value ($i.Value -as $i.TypeNameOfValue)
}

Note that passing the imported type name via the -Type parameter does not work for all types.