Add or Change Values to CSV - powershell

Question

I import a CSV in PowerShell, and want to export it again by either adding or changing content.
That's how I import it:
$csv = Import-Csv $csvFile -Delimiter ";"
The CSV has three colums, UserName, Pass and Key.
When I want to change one row:
$csv = $csv | ? { $_.UserName -eq $UserName } | % {
$_.pass = $PasName
$_.key = $KeyName
}
$csv | Export-Csv $csvFile -Delimiter ";" -Force -NoTypeInformation
it leaves me with a CSV without any content. Why is that?
Also, when I just want to add one row
$csv += [PSCustomObject]#{
UserName = $UserName
pass = $PasName
key = $KeyName
}
$csv | Export-Csv $csvFile -Delimiter ";" -Force -NoTypeInformation
it returns an error, saying:
Fehler beim Aufrufen der Methode, da [System.Management.Automation.PSObject] keine Methode mit dem Namen "op_Addition" enthält.
In Zeile:44 Zeichen:13
Does anybody know why this happens?
I know I could just add Content like so:
$xy = "{0};{1};{2}" -f xy,xy,xy
Add-Content -Path $csvFile -Value $xy
but I'd rather go with exporting the CSV completely new

Answer 1

Your second code snippet leaves you with an empty result because you assign the loop output back to the variable $csv. However, the loop does not produce any output, so you're effectively clearing the variable by doing that. To fix this simply remove the assignment. The loop updates the variable in-place.
$csv | Where-Object {
$_.UserName -eq $UserName
} | ForEach-Object {
$_.pass = $PasName
$_.key = $KeyName
}
$csv | Export-Csv $csvFile -Delimiter ";" -Force -NoTypeInformation
The error from your 3rd code snippet can occur if $csv is not an array (e.g. when it's empty or contains just a single record). You can mitigate that by forcing it to be an array upon import:
$csv = #(Import-Csv $csvFile -Delimiter ";")
Also, for appending a new record to your CSV it's cleaner and more straightforward to actually append to the CSV:
[PSCustomObject]#{
UserName = $UserName
pass = $PasName
key = $KeyName
} | Export-Csv $csvFile -Delimiter ";" -Force -NoTypeInformation -Append