ConvertTo-CliXml.ps1

function ConvertTo-CliXml {
    param(
        [Parameter(Position=0, Mandatory=$true, ValueFromPipeline=$true)]
        [ValidateNotNullOrEmpty()]
        [PSObject[]]$InputObject
    )
    begin {
        $type = [PSObject].Assembly.GetType('System.Management.Automation.Serializer')
        $ctor = $type.GetConstructor('instance,nonpublic', $null, @([System.Xml.XmlWriter]), $null)
        $sw = New-Object System.IO.StringWriter
        $xw = New-Object System.Xml.XmlTextWriter $sw
        $serializer = $ctor.Invoke($xw)
        #$method = $type.GetMethod('Serialize', 'nonpublic,instance', $null, [type[]]@([object]), $null)
    }
    process {
        try {
            [void]$type.InvokeMember("Serialize", "InvokeMethod,NonPublic,Instance", $null, $serializer, [object[]]@($InputObject))
        } catch {
            Write-Warning "Could not serialize $($InputObject.GetType()): $_"
        }
    }
    end {    
        [void]$type.InvokeMember("Done", "InvokeMethod,NonPublic,Instance", $null, $serializer, @())
        $sw.ToString()
        $xw.Close()
        $sw.Dispose()
    }
}