Walk an XML file, updating key values pairs based on a given pattern

Set-SeqNumToIncrementingValue.ps1

# Having generated well-formed but invalid xml from bsa xsd, the tool that gen'd the sample xml
# may have duplicated e.g. SeqNum.
# This takes an input file ($inFile), makes the SeqNum values unique, and writes to a random named
# file in c:/temp ($outFile).
# Now when you validate e.g. in Visual Studio or XMLSpy, the SeqNum will pass (even if plenty else is wrong.)
function Set-ReplacementString($templateStart, [int] $valueToUpdate, $templateEnd) {
    "$templateStart$valueToUpdate$templateEnd"
}

$inFile = Get-Content -Path C:\temp\x.xml
$inFile.Length

$pattern = "SeqNum=`".*`"" # "any and all characters within the double quotes are ignored for pattern-matching (in addition to SeqNum etc having to match)
$updatedPatternStart = "SeqNum=`""
$updatedPatternEnd = "`""

$r = [regex] $pattern
$currentSequenceNumber = 1
$filePrefix = Get-Random -Minimum 1 -Maximum 999999
$filePrefix
$outFile = "c:\temp\bsa_$filePrefix.xml"
$outFile
$inFile | ForEach-Object {
    $currentLine = $_
    $result = $r.Match($currentLine)
    if ($result.Success) {
        $foundLiteral = $result.Value
        # So $result.Value now becomes the literal string we want to replace
        "Found a pattern match: $foundLiteral"
        $replacementString = Set-ReplacementString $updatedPatternStart $currentSequenceNumber  $updatedPatternEnd
        $updatedLine = $currentLine -replace $foundLiteral, $replacementString
        $updatedLine

        $currentSequenceNumber++
        $updatedLine | Out-File -FilePath $outFile -Append
    }  else {
        $currentLine | Out-File -FilePath $outFile -Append
    }
}