Perform XML Validation using a Variable instead of File

Question

I'm using the code found here to perform XML validation:

function Test-Xml {
[cmdletbinding()]
param(
    [parameter(mandatory=$true)]$InputFile,
    $Namespace = $null,
    [parameter(mandatory=$true)]$SchemaFile
)

BEGIN {
    $failCount = 0
    $failureMessages = ""
    $fileName = ""
}

PROCESS {
    if ($inputfile)
    {
        write-verbose "input file: $inputfile"
        write-verbose "schemafile: $SchemaFile"
        $fileName = (resolve-path $inputfile).path
        if (-not (test-path $SchemaFile)) {throw "schemafile not found $schemafile"}
        $readerSettings = New-Object -TypeName System.Xml.XmlReaderSettings
        $readerSettings.ValidationType = [System.Xml.ValidationType]::Schema
        $readerSettings.ValidationFlags = [System.Xml.Schema.XmlSchemaValidationFlags]::ProcessIdentityConstraints -bor
            [System.Xml.Schema.XmlSchemaValidationFlags]::ProcessSchemaLocation -bor 
            [System.Xml.Schema.XmlSchemaValidationFlags]::ReportValidationWarnings
        $readerSettings.Schemas.Add($Namespace, $SchemaFile) | Out-Null
        $readerSettings.add_ValidationEventHandler(
        {
            try {
                $detail = $_.Message 
                $detail += "`n" + "On Line: $($_.exception.linenumber) Offset: $($_.exception.lineposition)"
            } catch {}
            $failureMessages += $detail
            $failCount = $failCount + 1
        });
        try {
            $reader = [System.Xml.XmlReader]::Create($fileName, $readerSettings)
            while ($reader.Read()) { }
        }
        #handler to ensure we always close the reader sicne it locks files
        finally {
            $reader.Close()
        }
    } else {
        throw 'no input file'
    }
}

It works fine and I can validate XML files when XML and XSD schema are "real files". Now suppose both are stored in Variables: I've replaced

$reader = [System.Xml.XmlReader]::Create($fileName, $readerSettings)

with

$reader = [System.Xml.XmlReader]::Create((new-Object System.IO.StringReader($String)), $readerSettings)

which DO WORK, but StringReader 'collapses' all the properly formatted XML File to a single line, and hence the any Validation error is always on line 1.

Is there a way to make [System.Xml.XmlReader] process a Variable instead of a File while preserving the Formatting stored in the Variable?

Many thanks

Answer 1

I don't think that you can preserve the formatting, but you can reformat it:

$StringWriter  = New-Object System.IO.StringWriter
$XmlTextWriter = New-Object System.XMl.XmlTextWriter $StringWriter
$XmlTextWriter.Formatting = "Indented"      # Default: None
$XmlTextWriter.Indentation = 2              # Default: 2
$XmlTextWriter.IndentChar = " "             # Default: Space
$String.WriteContentTo($XmlTextWriter)
"$StringWriter"