Cleaner PowerShell code for adding to array - arrays

Question

I'm trying to create a cleaner code for my script. I'm first defining the array, which will be used to check if the user account has been already queried. Currently the code has two nested if statements, which I want to combine into one if possible. Here is my code:
function addUser {
[cmdletbinding()]
Param(
[Parameter(Mandatory=$true)]
[String]$userName
,
[Parameter(Mandatory=$true)]
[String]$userDomain
,
[Parameter(Mandatory=$true)]
[String]$userAccount
)
Begin {}
Process {
$adAttribute = (Get-ADUser -Identity $userName -Server ($userDomain + "<FQDN HERE>") -Properties "<AD ATTRIBUTE NAME HERE>")."<AD ATTRIBUTE NAME HERE>"
Write-Output (
[pscustomobject]#{
userName = $userName
userDomain = $userDomain
userAccount = $userAccount
<AD ATTRIBUTE NAME HERE> = $adAttribute
}
)
}
End {}
}
$userList = #()
Get-Content $sourceFile | % {
<SOME CODE HERE>
if ($userList.Length -eq 0) {
$userList += addUser -userName $userName -userDomain $userDomain -userAccount $userAccount
}
else {
if (-not $userList.userAccount.Contains($userAccount)){
$userList += addUser -userName $userName -userDomain $userDomain -userAccount $userAccount
}
}
$userAdAttribute = $userList.Where({$_.userAccount -eq $userAccount})."<AD ATTRIBUTE NAME HERE>"
}
<SOME CODE HERE>
As you can see the following code is repetative:
$userList += <SOME FUNCTION CODE HERE>
but I cannot figure out how to make it cleaner, as in the beginning the array is empty and I cannot validate it before adding, so I'm wondering if anyone can share a tip?

Answer 1

I think you could do better using a Hashtable or HashSet for that instead of adding to an array with += (which needs to rebuild the entire array in memory on every addition)
$userList = #{}
$userAccount = <SOME CODE HERE>
# add the $userAccount you get from the code block above to the hash
if (-not $userList.Contains($userAccount)) {
# this user has not been processed, so do that here
<CODE TO PROCESS USER>
# next add to the Hashtable
$userList[$userAccount] = $true # the value is not important
}
Using a HashSet:
# on PowerShell below 5.0 use
# $userList = New-Object -TypeName 'System.Collections.Generic.HashSet[String]' -ArgumentList ([StringComparer]::InvariantCultureIgnoreCase)
$userList = [System.Collections.Generic.HashSet[string]]::new([StringComparer]::InvariantCultureIgnoreCase)
$userAccount = <SOME CODE HERE>
# add the $userAccount you get from the code block above to the hash
if (-not $userList.Contains($userAccount)) {
# this user has not been processed, so do that here
<CODE TO PROCESS USER>
# next add to the Hashtable
[void]$userList.Add($userAccount)
}
So, if it is not just about a string holding the userAccount (SamAccountName I gather), but about objects with multiple properties, you then need to use the Hashtable approach:
$userList = #{}
$userObject = <THE CODE THAT CALLS FUNCTION 'addUser' AND RETURNS THE USER OBJECT>
# add the $userObject you get from the code block above to the hash
if (-not $userList.Contains($userObject.userAccount)) {
# this user has not been processed, so do that here
<CODE TO PROCESS USER>
# next add to the Hashtable
$userList[$userObject.userAccount] = $userObject # the value is the userAccount Object
}