ConvertTo-DN

function ConvertTo-DN {
    <#
        .SYNOPSIS
        Convert a CanonicalName to a DistinguishedName
        .DESCRIPTION
        Takes an absolute CanonicalName value of an ActiveDirectory object and returns the corresponding DistinguishedName. The object must exist in AD.
        .PARAMETER  CanonicalName
        The CanonicalName value to examine. This can be supplied implicitly by piping an object that has a CanonicalName property.
        .PARAMETER  InputObject
        The object to manipulate. This parameter is typically passed to the function through the pipeline. If this parameter is supplied the -PropertyName parameter must also be specified.
        .PARAMETER  PropertyName
        The name of the property to add (as a NoteProperty) to the InputObject. This property will be set to the DistinguishedName value.
        .EXAMPLE
        'fabrikan.com/Users/Harden, Marsha Gay' | ConvertTo-DN
        CN=Harden\, Marsha Gay,OU=Users,DC=fabrikan,DC=com
        .EXAMPLE
        $ADOrgUnitObject | ConvertTo-DN -Property DN
        OU=TestOU,OU=Testing,DC=fabrikan,DC=com
        .INPUTS
        System.String, PSObject
        .OUTPUTS
        System.String, PSObject
        .NOTES
        Convertion is done by string manipulation alone, so the resulting DistinguishedName may or may not be valid.
        One cause of mismatch is leading 'CN=' may need to change to 'OU=' if the object is an Organizational Unit.
    #>
    [CmdletBinding(DefaultParameterSetName = 'None')]
    [Alias('ConvertTo-DistinguishedName', 'ConvertFrom-CanonicalName', 'ConvertFrom-CN')]
    [OutputType([string], ParameterSetName = "None")]
    [OutputType([PSObject], ParameterSetName = "InputObject")]
    Param (
        [Parameter(Mandatory, Position = 0, ValueFromPipeline, ValueFromPipelineByPropertyName, ParameterSetName = 'None')]
        [Alias('CN')][string[]]$CanonicalName,
        [Parameter(Mandatory, ValueFromPipeline, ParameterSetName = 'InputObject')][PSObject[]]$InputObject,
        [Parameter(Mandatory, ParameterSetName = 'InputObject')][string]$PropertyName = 'DN'
    )
    begin {
        [boolean]$PipelineInput = -not $PSBoundParameters.ContainsKey("CanonicalName")
        $HexMap = @{}
        1..31 | % { $HexMap[('\x' + $_.ToString('X2'))] = '\' + $_.ToString('X2') }
        function CDN {
            [CmdletBinding()]
            Param ([Parameter(Position = 0, Mandatory)][string]$CN)
            # first we split on backslash (but only if not escaped),
            # then we escape those characters that need escaping in a DistinguishedName.
            trap { return }
            [System.Collections.ArrayList]$Obj = @(($CN -split '(?<!\\)/') | % { ($_ -replace '\\/', '/') -replace '(\A\s|(?<!\\)\\(?!\\)|[,#+<>;"=]|\s\z)', '\$1' })
            # replace non-printable characters
            foreach ($k in $HexMap.Keys) { $Obj = $Obj -replace $k, $HexMap[$k] }
            [string]$DC = ',DC=' + (($Obj[0] -split '\.') -join ',DC=')
            if ($Obj.Count) { [void]$Obj.RemoveAt(0); [void]$Obj.Reverse() }
            [string]$DN = if ($Obj.Count) { 'CN=' + $Obj[0]; [void]$Obj.RemoveAt(0) } else { '' }
            $DN += if ($Obj.Count) { ',OU=' + ($Obj -join ',OU=') + $DC } else { $DC }
            $DN = $DN -replace ",OU=(Users|Computers|Deleted Objects|ForeignSecurityPrincipals|LostAndFound|System|Builtin|Microsoft Exchange System Objects),DC=", ',CN=$1,DC='
            $DN -replace '\A,'
        }
    }
    PROCESS {
        if ($PipelineInput) {
            if ($PSBoundParameters.ContainsKey('PropertyName')) {
                foreach ($o in $InputObject) {
                    $DN = CDN -CN $o.CanonicalName
                    $o | Add-Member -NotePropertyName $PropertyName -NotePropertyValue $DN -Force -PassThru
                }
            } else {
                CDN -CN $CanonicalName[0]
            }
        } else {
            foreach ($CN in $CanonicalName) {
                CDN -CN $CN
            }
        }
    }
} # ConvertTo-DN