Replace CRLF in file - powershell

Question

I am actually trying to make a .txt file looking like this:
text1
text 2
text3
text4
in something like this:
text1,text2
text3,text4
I have tried a lot of things, like:
foreach($line in $file){
$line=$line -replace'`r`n', ','
}
Or directly by replacing in the file and not the string:
$file=Get-Content('testo.txt')
$file=$file -replace '`r`n',''
But nothing worked. I have never been able to replace the CRLF.
If someone has an idea or anything!

Answer 1

Something even simpler I think. This would depend on the size of the text file since it has to be all read into memory. However this would will work with variable lines of "test" data and white space. I am going to assume that your data does not already contain commas.
$file = (Get-Content "c:\temp\data.txt") -join "," -replace ",{2,}","`r`n"
Set-Content -Path "C:\temp\Newfile.txt" -Value $file
Take the file and convert it into a comma delimited string. What will happen is that you will see a series of groups commas. Using your test data
text1,text 2,,,text3,text4
The we use regex to replace and consecutive comma groups of 2 or more with newlines. Getting the desired output.
text1,text 2
text3,text4

Answer 2

In fact i have done something like this:
$Writer = New-Object IO.StreamWriter "$($PWD.Path)\$OutputFile"
$Writer.Write( [String]::Join(".", $data) )
$Writer.Close()
$data=get-content temp.txt
$data=$data -replace '[#]{2,}',"`r`n"
$data=$data -replace '[#]',","
$data=$data -replace '( ){1,},',"no data"
$data>>temp1.txt
It works and do what I want. It is not exactly efficient, but I wanted it to work quickly.
I will try all the answers when I have the time and say if it works or not.
And maybe I will change this part of my script if I find something more efficient.
Thanks to all!