CSV file editing using PowerShell

Question

I need to do below using PowerShell scripting.

I have the below data in CSV file. I need to append another prefix to the name according to the subject supplied

Name,Subject,Roll,Div
Mark,Agri,3,Div1,
Tom,CS,6,Div3,
Alex,Aero,9,Div6

Suppose i am supplied the subject as Agri, the name should have prefix as P-. So the same CSV file will be saved and have below content

Name,Subject,Roll,Div
P-Mark,Agri,3,Div1,
Tom,CS,6,Div3,
Alex,Aero,9,Div6

Here's what I have so far:

(Import-Csv E:\Test.csv -Delimiter ',') | ForEach-Object{

    if($_.Subject -match "Agri" )
    {
      $_ = "P-" + "$_";

    }
    else
    {
     $_ = "F-" + "$_";

    }

} | Export-Csv E:\Test.csv -Delimiter ',' 

Answer 1

I wasn't able to pipe this together - might just be ignorance on my part about powershell syntax. I was able to do it with the following using two lines:

($csv = Import-Csv E:\Test.csv -Delimiter ',') | ForEach {
    if ($_.Subject -match "Agri") {
        $_.Name = 'P-' + $_.Name
    } else {
        $_.Name = 'F-' + $_.Name
    }

}
$csv | Export-Csv E:\Test.csv -Delimiter ',' -NoType

Notice:

$_ = "P-" + $_;

Becomes

$_.Name = "P-" + $_.Name;

Answer 2

It seems to me the use of paren's in the following clause.

($csv = Import-Csv E:\Test.csv -Delimiter ',')

will assign to $csv the output of Import-Csv PRIOR to the ForEach processing and therefore the ForEach effects are completely lost. Not sure what you purpose is in using those paren's.