XmlFileTreeGenerators.ps1

function Get-XmlFileTreeAppend
{
    param(
        [Parameter(ParameterSetName='Path', Mandatory=$true, Position=0, ValueFromPipeline=$true, ValueFromPipelineByPropertyName=$true)]
        [string[]]
        ${Path},
    
        [Parameter(ParameterSetName='LiteralPath', Mandatory=$true, ValueFromPipelineByPropertyName=$true)]
        [Alias('PSPath')]
        [string[]]
        ${LiteralPath}
    )

    function ProcessNode
    {
        param([System.IO.FileSystemInfo]$item,[System.Xml.XmlNode]$parent)

        $doc = if(!$parent.OwnerDocument){
            $parent
        }
        else{
            $parent.OwnerDocument
        }

        if($item -is [System.IO.DirectoryInfo]) {
            $newNode = $doc.CreateElement('Directory')
            $newNode.SetAttribute('Name', $item.Name)

            $item.EnumerateDirectories() |ForEach-Object {
                ProcessNode $_ $newNode
            }

            $item.EnumerateFiles() |ForEach-Object {
                ProcessNode $_ $newNode
            }
        }
        else {
            $newNode = $doc.CreateElement('File')
            $newNode.SetAttribute('Name', $item.Name)
            $newNode.SetAttribute('Size', $item.Length)
        }
        [void]$parent.AppendChild($newNode)
    }

    $root = Get-Item @PSBoundParameters
    $xml = [xml]::new()
    ProcessNode $root $xml

    return $xml.OuterXml
}

function Get-XmlFileTreeWriter
{
    param(
        [Parameter(ParameterSetName='Path', Mandatory=$true, Position=0, ValueFromPipeline=$true, ValueFromPipelineByPropertyName=$true)]
        [string[]]
        ${Path},
    
        [Parameter(ParameterSetName='LiteralPath', Mandatory=$true, ValueFromPipelineByPropertyName=$true)]
        [Alias('PSPath')]
        [string[]]
        ${LiteralPath}
    )

    function NewNode
    {
        param([System.IO.FileSystemInfo]$item,[System.Xml.XmlWriter]$writer)

        $isDir = $item -is [System.IO.DirectoryInfo]

        if($isDir) {
            $writer.WriteStartElement('Directory')
            $writer.WriteAttributeString('Name',$item.Name)

            $item.EnumerateDirectories() |ForEach-Object {
                NewNode $_ $writer
            }

            $item.EnumerateFiles() |ForEach-Object {
                NewNode $_ $writer
            }
        }
        else {
            $writer.WriteStartElement('File')
            $writer.WriteAttributeString('Name', $item.Name)
            $writer.WriteAttributeString('Size', $item.Length)
        }
        $writer.WriteEndElement()
    }

    try{
        $settings = [System.Xml.XmlWriterSettings]@{ Indent = $true; Encoding = [System.Text.Encoding]::UTF8 }
        $stringbuilder = [System.Text.StringBuilder]::new()
        $writer = [System.Xml.XmlWriter]::Create($stringbuilder, $settings)

        $writer.WriteStartDocument()
        NewNode (Get-Item @PSBoundParameters) $writer
        $writer.WriteEndDocument()

        $writer.Flush()

        return $stringbuilder.ToString()
    }
    finally {
        if($writer -is [IDisposable]){
            $writer.Dispose()
        }
    }
}