Iterating over multiple find and replace object - powershell

Question

I know the solution below is quite simple but I am not able to get it to work. I created an object with a find and replace string property. The goal to replace all strings in the text file but it is not working properly. The code below would only replace the last object in the list. I've searched several stack over flow questions but was only able to find multiple files, not multiple find/replace strings.
Input File:
TEMPERATURE 1
TEMPERATURE 2
AVERAGE 1
AVERAGE 2
Expected Output:
TEMP 1
TEMP 2
AVG 1
AVG 2
Actual Output:
TEMP 1
TEMP 2
AVERAGE 1
AVERAGE 2
class FindReplace {
[string]$FindString;
[string]$ReplaceString;
}
[System.Collections.Generic.List[FindReplace]]$FindReplaceList = #()
$Obj1 = New-Object FindReplace
$Obj1.FindString = "AVERAGE"
$Obj1.ReplaceString = "AVG"
$Obj2 = New-Object FindReplace
$Obj2.FindString = "TEMPERATURE"
$Obj2.ReplaceString = "TEMP"
$FindReplaceList.Add($Obj1);
$FindReplaceList.Add($Obj2);
write-host $FindReplaceList.Count
for($i = 0; $i -lt $FindReplaceList.Count; $i++)
{
Write-Host "Replacing string" $FindReplaceList[$i].FindString "to" $FindReplaceList[$i].ReplaceString " where input file:" $inputTextFilePath "and output file:" $outputTextFilePath
(Get-Content $inputTextFilePath).Replace($FindReplaceList[$i].FindString, $FindReplaceList[$i].ReplaceString) | Set-Content $outputTextFilePath
}

Answer 1

As #AdminOfThings mentioned in the comments. The problem is that you are reading the file once, and then writing twice. So you don't end up with all of the replacements like you are expecting.
See below. I've done a little bit of cleanup, but this is what you could do...
I'm reading the contents of the file into memory once, storing it as a variable. Then performing the replacements on the variable, and then writing the contents of the variable to file:
$inputTextFilePath = 'D:\StackOverflow\fart\test.txt'
$outputTextFilePath = 'D:\StackOverflow\fart\test_output.txt'
class FindReplace {
[string]$FindString;
[string]$ReplaceString;
}
[System.Collections.Generic.List[FindReplace]]$FindReplaceList = #()
$Obj1 = New-Object FindReplace
$Obj1.FindString = "AVERAGE"
$Obj1.ReplaceString = "AVG"
$Obj2 = New-Object FindReplace
$Obj2.FindString = "TEMPERATURE"
$Obj2.ReplaceString = "TEMP"
$FindReplaceList.Add($Obj1);
$FindReplaceList.Add($Obj2);
write-host $FindReplaceList.Count
$fileContent = Get-Content $inputTextFilePath;
foreach ($item in $FindReplaceList)
{
Write-Host "Replacing string $($item.FindString) to $($item.ReplaceString) where input file: $inputTextFilePath and output file: $outputTextFilePath";
$fileContent = $fileContent.Replace($item.FindString, $item.ReplaceString);
}
Set-Content -Value $fileContent -Path $outputTextFilePath;
And of course, since "[F]ind [A]nd [R]eplace [T]ext" questions only come up every so often...I had to make use of that fancy acronym :)