How do I use PowerShell to Validate XML files against an XSD?

As a part of my development I'd like to be able to validate an entire folder's worth of XML files against a single XSD file. A PowerShell function seems like a good candidate for this as I can then just pipe a list of files to it like so: dir *.xml | Validate-Xml -Schema .\MySchema.xsd

I've considered porting C# code from the Validating an Xml against Referenced XSD in C# question, but I don't know how to Add handlers in PowerShell.

I wrote a PowerShell function to do this:

Usage:

dir *.xml | Test-Xml -Schema ".\MySchemaFile.xsd" -Namespace "http://tempuri.org"

Code:

function Test-Xml {
    param(
        $InputObject = $null,
        $Namespace = $null,
        $SchemaFile = $null
    )

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

    PROCESS {
        if ($InputObject -and $_) {
            throw 'ParameterBinderStrings\AmbiguousParameterSet'
            break
        } elseif ($InputObject) {
            $InputObject
        } elseif ($_) {
            $fileName = $_.FullName
            $readerSettings = New-Object -TypeName System.Xml.XmlReaderSettings
            $readerSettings.ValidationType = [System.Xml.ValidationType]::Schema
            $readerSettings.ValidationFlags = [System.Xml.Schema.XmlSchemaValidationFlags]::ProcessInlineSchema -bor
                [System.Xml.Schema.XmlSchemaValidationFlags]::ProcessSchemaLocation -bor 
                [System.Xml.Schema.XmlSchemaValidationFlags]::ReportValidationWarnings
            $readerSettings.Schemas.Add($Namespace, $SchemaFile) | Out-Null
            $readerSettings.add_ValidationEventHandler(
            {
                $failureMessages = $failureMessages + [System.Environment]::NewLine + $fileName + " - " + $_.Message
                $failCount = $failCount + 1
            });
            $reader = [System.Xml.XmlReader]::Create($_, $readerSettings)
            while ($reader.Read()) { }
            $reader.Close()
        } else {
            throw 'ParameterBinderStrings\InputObjectNotBound'
        }
    }

    END {
        $failureMessages
        "$failCount validation errors were found"
    }
}