remove only blanks line by line with user input - csv

Question

Yesterday I asked this question. Now I would like to do almost the same exercise with a small change: if there is a blank character on a line (go line by line in the CSV) ask the user if the blank character should be removed or not; the difference is, ONLY the blank and not the whole line.
The code which works for my previous question is:
$yes = New-Object System.Management.Automation.Host.ChoiceDescription "&Yes", "Retain line."
$no = New-Object System.Management.Automation.Host.ChoiceDescription "&No", "Delete line."
$n = #()
$f = Get-Content .\test.csv
foreach ($item in $f) {
if($item -like "* *"){
$res = $host.ui.PromptForChoice("Title", "want to keep this line? `n $item", [System.Management.Automation.Host.ChoiceDescription[]]($yes, $no), 0)
switch ($res) {
0 {$n+=$item}
1 {}
}
} else {
$n+=$item
}
}
$n | Set-Content .\test.csv
What I think I should use is the Trim() function to achieve this.
So, I think I should modify in the if clause like below (aplogies for the silly syntax mistakes which I might do):
$yes = New-Object System.Management.Automation.Host.ChoiceDescription "&Yes", "Retain blank."
$no = New-Object System.Management.Automation.Host.ChoiceDescription "&No", "Delete blank."
$n = #()
$f = Get-Content .\test.csv
foreach ($item in $f) {
if ($item -like "* *") {
$res = $host.ui.PromptForChoice("Title", "want to keep the blank on this line? `n $item", [System.Management.Automation.Host.ChoiceDescription[]]($yes, $no), 0)
switch ($res) {
0 {$n+=$item.Trim()}
1 {}
}
} else {
$n+=$item.Trim()
}
}
$n | Set-Content .\test.csv
This runs, but still deteles the line, so it shouldn't matter if I trimmed it or not first, I need to fix it so it will be kept or trimmed but not discarded .
EDIT:
Adjusting the switch ($res) like this doesn't work:
switch ($res) {
0 {$n+=$item.Trim()}
1 {$n+=$item}
}
} else {
$n+=$item.Trim()
}

Answer 1

Trim() without parameter removes all whitespace (not just spaces) from beginning and end of a string. You can't use it for removing spaces anywhere else in a string. Instead use the -replace operator:
$_ -replace ' '
Note that this time you need to output the unmodified string not only if it doesn't contain a space, but also if the user chooses to keep the existing space(s).