Powershell - Combine CSV files and append a column - powershell

Question

I'm trying (badly) to work through combining CSV files into one file and prepending a column that contains the file name. I'm new to PowerShell, so hopefully someone can help here.
I tried initially to do the well documented approach of using Import-Csv / Export-Csv, but I don't see any options to add columns.
Get-ChildItem -Filter *.csv | Select-Object -ExpandProperty FullName | Import-Csv | Export-Csv CombinedFile.txt -UseQuotes Never -NoTypeInformation -Append
Next I'm trying to loop through the files and append the name, which kind of works, but for some reason this stops after the first row is generated. Since it's not a CSV process, I have to use the switch to skip the first title row of each file.
$getFirstLine = $true
Get-ChildItem -Filter *.csv | Where-Object {$_.Name -NotMatch "Combined.csv"} | foreach {
$filePath = $_
$collection = Get-Content $filePath
foreach($lines in $collection) {
$lines = ($_.Basename + ";" + $lines)
}
$linesToWrite = switch($getFirstLine) {
$true {$lines}
$false {$lines | Select -Skip 1}
}
$getFirstLine = $false
Add-Content "Combined.csv" $linesToWrite
}

Answer 1

This is where the -PipelineVariable parameter comes in real handy. You can set a variable to represent the current iteration in the pipeline, so you can do things like this:
Get-ChildItem -Filter *.csv -PipelineVariable File | Where-Object {$_.Name -NotMatch "Combined.csv"} | ForEach-Object { Import-Csv $File.FullName } | Select *,#{l='OriginalFile';e={$File.Name}} | Export-Csv Combined.csv -Notypeinfo

Answer 2

Merging your CSVs into one and adding a column for the file's name can be done as follows, using a calculated property on Select-Object:
Get-ChildItem -Filter *.csv | ForEach-Object {
$fileName = $_.Name
Import-Csv $_.FullName | Select-Object #{
Name = 'FileName'
Expression = { $fileName }
}, *
} | Export-Csv path/to/merged.csv -NoTypeInformation